STUDIES ON THE DIGESTIBILITY OF ORCHARD GRASS

WITH DAIRY CATTLE

I* A comparison o f seireral techniques for determ ining d ig e s t ib i l ­

i t y c o e f f ic ie n t s w ith dairy c a t t l e .

I I . S tud ies on the com position o f l ig n in is o la te d from orchard

grass hay cu t a t four stages o f m aturity and from the corres­

ponding feces*

I I I . A study o f the crude f ib e r and n itro g en -free ex tra ct fr a c tio n s

o f orchard grass hay and the d ig e s t ib i l i t y o f some o f the con­

s t itu e n ts by m ilk ing cows.

by

Ray E* E ly

A THESIS

Presented to the Graduate School o f Michigan S tate C ollege o f

A gricu lture and Applied Science in p a r t ia l fu lf i l lm e n t

o f the requirements for the degree o f

DOCTOR OF PHILOSOPHY

Dairy Department

E ast Lansing, Michigan

1952

ACKNOWLEDGMENTS

The w riter w ishes to express h is most sin cere ap p reciation

to Dr. C. P. Huffman, Research P rofessor in Dairy Husbandry, and

to Dr. L. A. Moore, Head o f the D iv is io n o f N u tr itio n and Physi­

o logy , Bureau o f Dairy Industry, B e l t s v i l l e , Maryland, fo r th e ir

In sp ira tio n and cooperation in the planning o f t h i s in v e s t ig a tio n ;

for th e ir advice and c r it ic ism s during the preparation o f t h is

manuscript; and for providing the necessary f a c i l i t i e s for the

conduct o f these s tu d ie s . The author lik ew ise w ishes to express

h is appreciation to Mr. E. A. Kane and Mr. W. C. Jacobson,

Chemists, Bureau o f Dairy Industry, for th e ir in te r e s t and aid

w ith c er ta in o f the chemical a n a ly ses. Gratitude i s a lso ex­

pressed to Dr. Earl Weaver, Head, Dairy Department, fo r h is

in te r e s t and encouragement during the course o f these s tu d ie s .

FORWARD

The r e s u lt s reported in th is th e s is were secured from in v e s t­

ig a tio n s conduoted over a period o f the p ast three years#

In order to s im p lify p resen ta tio n , the re s t ilt s have been

divided in to three parts# part I was an in v e s t ig a t io n o f several

d iffe r e n t techniques fo r determ ining the d ig e s t ib i l i t y c o e f f ic ie n t s

o f forage fo r dairy c a t t le studied w ith orchard grass hay cu t a t

four stages o f maturity# Part I I was a study o f the d ig e s t ib i l i t y

o f l ig n in in orchard grass hays out a t various stages o f m aturity

and an in v e s t ig a tio n o f the com position o f the l ig n in is o la te d

from these orchard grass hays and the corresponding feces# In

Part I I I a more d e ta ile d a n a ly s is was made o f the crude f ib e r and

n itr o g en -fr ee ex tra ct fra c tio n s and the d ig e s t ib i l i t y o f the

various co n stitu e n ts reported .

STUDIES ON THE DIGESTIBILITY OP ORCHARD

GRASS WITH DAIRY CATTLE

By

Ray E. Ely

AN ABSTRACT

Submitted to the School o f Graduate S tudies o f Michigan

State C ollege o f A gricu lture and Applied Science

in p a r t ia l fu lf i l lm e n t o f the requireotnents

for the degree o f

DOCTOR OF PHILOSOPHY

Dairy Department

1952

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2

STUDIES ON THE DIGESTIBILITY OF ORCHARD GRASS

WITH DAIRY CATTLE

A comparison o f severa l techniques for determ ining d ig e s t ib i l i t y

c o e f f ic ie n t s w ith dairy c a t t le was made w ith four stages o f orchard

grass hay fed to three m ilking cows* D ig e s t ib i l i t y c o e f f ic ie n t s c a l­

cu la ted by the conventional ten day consum ption-excretion r a t io s were

compared w ith the c o e f f ic ie n t s ca lcu la ted by the chromium, l ig n in

and p lant pigment r a tio techniques w ith the t o t a l c o lle c t io n samples

and a lso w ith p a r t ia l c o lle c t io n s or "grab* samples*

Comparable d ig e s t io n c o e f f ic ie n t s were secured w ith the standard

ten day consum ption-excretion method and the chromium and p lan t p ig ­

ment r a tio techniques* D igestion c o e f f ic ie n t s ca lcu la ted by the

crude l ig n in and the corrected l ig n in r a tio techniques u sin g the

t o t a l f e c a l c o l le c t io n samples were both s ig n if ic a n t ly lower than

the d ig e s t io n c o e f f ic ie n t s ca lcu la ted by the standard consumption-

ex cre tio n method.

D ig e s t ib i l i t i e s o f the various co n stitu e n ts in the four stages

o f orchard grass hay o f in creasin g m aturity were; dry m atter, 6 9 .0 ,

70*4, 63*9 and 59*4 percent; p r o te in , 65*7, 60*7, 55*4 and 54*3 per­

cen t; crude f ib e r , 8 2*5, 78*6, 72*0 and 69.1 percent; and n itrogen -

fre e e x tr a c t , 6 9 .3 , 74*7, 68.0 and 57.3 p ercen t, r e sp e c t iv e ly .

The apparent d ig e stio n c o e f f ic ie n t s o f l ig n in in the orchard

grass hays fed ranged from 3.8 to 16.0 p ercen t. The l ig n in I so la te d

from the four sta g es o f orchard grass o f in creasin g m aturity had

n itrogen contents o f 4 .2 5 , 4 .1 5 , 3 .53 and 2.41 p ercen t. The average

n itrogen contents o f the l ig n in iso la te d from the corresponding

fe c e s were 5 .1 9 , 4 .1 3 , 3.62 and 2.91 percent.

5

The benzoic ac id excretion in the urine per 100 grams o f l ig n in

fed was lower when feeding the most mature hay than when feed in g the

other th ree l e s s mature hays. There was no r e la t io n between the d ig e s­

t io n c o e f f ic ie n t s o f l ig n in and the urinary ex cretio n o f benzoic acid*

The to ta l raetboxyl content o f the hay fed was lower than the to ­

t a l methoxyl content o f the corresponding fe c e s on a dry matter basis*

The methoxyl conten ts o f the l ig n in iso la te d from the various hays

was higher than the methoxyl conten ts o f the lig n in is o la te d from

the cerresponding feces*

D ig e s t ib i l i t y o f the to ta l methosyl content and the n o n -lig n in

methoxyl content o f the r a tio n decreased w ith in creasin g m aturity o f

the orchard grass hay* D igestion o f the l ig n in methoxyl groups ranged

from 20*3 to 31*6 percent and showed no c o n sisten t trend in r e la t io n

to the stage o f m aturity o f the hay fed*

A more d e ta iled system o f a n a ly s is th a t included determ inations

o f the starch , sugars, organic a c id s , pentosans, alpha c e l lu lo s e , and

l ig n in on the orchard grass hays and the corresponding fe c e s was used

to study the c o n stitu en ts o f the crude f ib e r and n itro g en -free e x tr a c t

fraction s*

This system o f a n a ly s is accounted for a greater percentage o f the

dry m atter o f the immature orchard grass hay than with the more mature

orchard grass hay. Higher percentages o f the dry m atter were a lso de­

termined in the fe c e s o f animals fed the immature orchard grass hay

than in the fec es o f animals fed the mature orchard grass hay. Con­

sid erab ly higher percentages o f the t o t a l dry matter o f fe c e s were

determined by th is system o f a n a ly s is than were determined w ith the

same a n a ly tic a l techniques on the forage fed these anim als.

TABLE OF CONTENTS

PART I .

A COMPARISON OF SEVERAL TECHNIQUES FOR DETERMINING DIGESTIBILITY

COEFFICIENTS WITH DAIRY CATTLE.

INTRODUCTION 1

REVIEW OF LITERATURE 3

DIGESTION TRIAL TECHNIQUES 3

Total F eca l C o llec tio n Technique 3Chromic Oxide Ratio Technique 4L ignin R atio Technique 9In d ig e st ib le P ro te in Ratio Technique 14Iron Ratio Technique 15S i l i c a R atio Technique 17Plant Pigment Ratio Technique 18Other D igestion T r ia l Techniques 21

FACTORS AFFECTING THE DIGESTIBILITY OF ROUGHAGES 23

E ffe c t o f Crude F iber on D ig e s t ib i l i t y 23E ffe c t o f C e llu lo se Content on D ig e s t ib i l i t y 32E ffe c t o f Lignin Content on D ig e s t ib i l i t y 36E ffe c t o f Methoxyl Content o f P lan ts on D ig e s t ib i l i t y 39E ffe c t o f Stage o f M aturity on D ig e s t ib i l i t y 41E ffec t o f P lant Ash on D ig e s t ib i l i t y 45A sso c ia tiv e E ffe c t o f Feeds and D ig e s t ib i l i t y 47E ffe c t o f A n tib io tic s on D ig e s t ib i l i t y 50

SUMMARY OF THE REVIEW OF LITERATURE 53

PLAN OF EXPERIMENT AND METHODS USED 54

EXPERIMENTAL RESULTS AND DISCUSSION 61

SUMMARY 65

LITERATURE CITED 67

PART I I

STUDIES ON THE COMPOSITION OF LIGNIN ISOLATED FROM ORCHARD GRASS

HAY CUT AT FOUR STAGES OF MATURITY AND FROM THE CORRESPONDING FECES.

INTRODUCTION 97

EXPERIMENTAL PROCEDURE 99

RESULTS AND DISCUSSION 100

SUMMARY 104

LITERATURE CITED 106

TABLES 110

PART I I I

A STUDY OF THE CRUDE FIBER AND NITROGEN-FREE EXTRACT FRACTIONS OF

ORCHARD GRASS HAY AND THE DIGESTIBILITY OF SOME OF THE CONSTITUENTS

BY MILKING COWS.

INTRODUCTION 116

EXPERIMENTAL PROCEDURE 120

RESULTS AND DISCUSSION 121

SUMMARY 126

TABLES 133

PART I

A COMPARISON OF SEVERAL TECHNIQUES FOR DETERMINING

DIGESTIBILITY COEFFICIENTS WITH DAIRY CATTLE

INTRODUCTION

One o f t h e m o s t common m e th o d s u s e d t o e v a l u a t e t h e n u t r i t i v e v a l u e

o f f e e d s i s t o d e t e r m i n e t h e i r d i g e s t i b l e n u t r i e n t c o n t e n t* C o m p i l a t i o n

o f t h e a v e r a g e p r o x i m a t e c o m p o s i t io n * a v e r a g e d i g e s t i o n c o e f f i c i e n t s *

and a v e r a g e t o t a l d i g e s t i b l e n u t r i e n t c o n t e n t v a l u e s f o r a l a r g e num ber

o f f e e d s h av e b e e n made by M o r r i s o n (1 2 6 ) and S c h n e i d e r ( 1 6 1 ) . T ih ile

t h e s e a v e r a g e v a l u e s a r e i n many i n s t a n c e s d e r i v e d f ro m a l a r g e num b er

o f t r i a l s * many a r e o f n e c e s s i t y t a k e n f ro m a l i m i t e d num ber o f t r i a l s

and p e r h a p s f o r a s i n g l e s p e c i e s . Many r e s e a r c h -w orkers n e e d t o know t h e

d i g e s t i b l e n u t r i e n t c o n t e n t o f a g iv e n f e e d f o r s p e c i f i c a n i m a l s u n d e r

c e r t a i n c o n t r o l l e d c o n d i t i o n s o r u n d e r w i d e l y v a r y i n g c o n d i t i o n s . F o r

ex am ple* i t i s d e s i r a b l e t o know t h e n u t r i t i v e v a l u e o f v a r i o u s p a s t u r e

m i x t u r e s u n d e r w i d e l y v a r y i n g c o n d i t i o n s o f r a i n f a l l , t e m p e r a t u r e * s o i l

t y p e s * s o i l t r e a t m e n t s * and g r a z i n g m anagem ent w i t h d i f f e r e n t a n i m a l s

w h ic h v a r y q u i t e w i d e l y i n t h e i r n u t r i t i v e r e q u i r e m e n t . S c h n e i d e r e t a l .

(1 6 5 ) a n a l y z e d t h e p u b l i s h e d d a t a f o r f i v e c l a s s e s o f f e e d s f e d t o f o u r

s p e c i e s o f a n im a ls t o d e t e r m in e t h e v a l u e o f a v e r a g e d i g e s t i b i l i t y d a t a

I n d e t e r m i n i n g t h e n u t r i t i v e v a l u e o f p a r t i c u l a r f e e d s a m p le s . They c o n ­

c l u d e d t h a t t h e p r a c t i c e o f a p p l y i n g a v e r a g e d i g e s t i o n c o e f f i c i e n t s f o r a

g iv e n f e e d t o p a r t i c u l a r s a m p le s o f t h a t f e e d i s w a r r a n t e d d e s p i t e t h e

f a c t t h a t a h i g h w i t h i n - f e e d v a r i a b i l i t y i n d i g e s t i b i l i t y o c c u r s . S c h n e i d e r

and L u c a s ( 1 6 3 ) a l s o s t u d i e d p u b l i s h e d d i g e s t i b i l i t y d a t a t o d e t e r m i n e

t h e r e l a t i v e m a g n i tu d e o f c e r t a i n s o u r c e s o f v a r i a t i o n . They fo u n d t h a t

25 t o 45 p e r c e n t o f t h e w i t h i n - f e e d v a r i a n c e i n d i g e s t i b i l i t y I s a s s o ­

c i a t e d w i t h v a r i a t i o n s i n p r o x i m a t e c o m p o s i t io n * 20 t o 40 p e r c e n t o .sso-

c i a t e d w i t h a u t h o r s , 20 t o 35 p e r c e n t a s s o c i a t e d w i t h s a m p le s o f f e e d

2

and 10 "to 25 p e r c e n t a s s o c i a t e d w i t h t h e t r i a l . They p o i n t e d o u t t h a t

a v e r a g e d i g e s t i o n c o e f f i c i e n t s s h o u ld he a d j u s t e d f o r t h e p r o x i m a t e com­

p o s i t i o n o f t h e p a r t i c u l a r sam p le b e i n g u s e d . They a l s o s u g g e s t e d t h a t

a g r e a t e r am ount o f t h e v a r i a n c e c o u ld be r e l a t e d t o c o m p o s i t i o n o f t h e

f e e d i f o t h e r n u t r i e n t s , i n a d d i t i o n t o t h o s e d e t e r m i n e d i n t h e u s u a l

p r o x i m a t e a n a l y s i s , w e re a s c e r t a i n e d .

I n t e r e s t i n t h e s o - c a l l e d i n e r t m a t e r i a l " r a t i o t e c h n i q u e s " o f

d e t e r m i n i n g t h e d i g e s t i b i l i t y o f t h e v a r i o u s c o n s t i t u e n t s o f f e e d h a s

b e e n s t i m u l a t e d l a r g e l y by t h e f a c t t h a t i t w i l l p e r m i t d i g e s t i o n t r i a l

s t u d i e s t o be made u n d e r t h e same c o n d i t i o n s an d w i t h t h e same a n i m a l s

t h a t w o u ld n o r m a l l y be u se d f o r t h e f e e d i n v e s t i g a t e d . F u r t h e r m o r e ,

a d d i t i o n o f an i n e r t m a t e r i a l t o t h e d a i l y r a t i o n o f a g r a z i n g a n i m a l

w o u ld p e r m i t c a l c u l a t i o n o f t h e d a i l y d r y m a t t e r e x c r e t i o n f ro m wg r a b H

s a m p le s c o l l e c t e d a t c o n v e n i e n t i n t e r v a l s . The d e t e r m i n a t i o n o f t h e

c o n c e n t r a t i o n o f a n i n e r t n a t u r a l l y - o c c u r r i n g c o n s t i t u e n t o f t h e f e e d

on b o t h t h e f e e d and f e c e s s a m p le s w o u ld n e r m i t a c a l c u l a t i o n o f t h e

d r y m a t t e r i n t a k e o f t h e a n im a l s t u d i e d and c a l c u l a t i o n o f t h e d r y

m a t t e r d i gc s t i h i 1 i t y •

The u s e o f t h e i n e r t m a t e r i a l r a t i o t e c h n i q u e f o r d e t e r m i n i n g t h e

d i g e s t i b i l i t y o f a f e e d o r r a t i o n w ould f a c i l i t a t e s t u d i e s o f v a r i o u s

f e e d s w i t h d i f f e r e n t s p e c i e s an d u n d e r w i d e l y v a r y i n g c o n d i t i o n s t h a t

a r e n o t r e a d i l y f e a s i b l e w i t h t h e c o n v e n t i o n a l t o t a l f e c a l c o l l e c t i o n

t e c h n i q u e , i f d i r e c t c o m p a r i s o n s c o u ld be e s t a b l i s h e d b e tw e e n t h e s e

m e th o d s .

REVIEW OF LITERATURE

DIGESTION TRIAL TECHNIQUES

T o t a l F e c a l C o l l e c t i o n T e c h n iq u e

D i g e s t i o n t r i a l t e c h n i q u e s i n v o l v i n g t h e t o t a l c o l l e c t i o n o f f e c e s

o v e r a s p e c i f i e d p e r i o d o f t im e w h i l e t h e a n i m a l s a r e on a c o n s t a n t f e e d

i n t a k e and c a l c u l a t i o n o f t h e d i g e s t i b i l i t y o f t h e v a r i o u s n u t r i e n t s f r o m

t h e n u t r i e n t i n t a k e - e x c r o t i o n r a t i o n h a v e c h a n g e d b u t l i t t l e s i n c e t h e i r

a d o p t i o n by H e n n e b e rg and S tohm ann ( 9 1 ) .

The l e n g t h o f t h e c o l l e c t i o n p e r i o d i n d i g e s t i o n t r i a l s u s i n g t o t a l

f e c a l c o l l e c t i o n s f o r s e c u r i n g s a t i s f a c t o r y d i g e s t i b i l i t y c o e f f i c i e n t s i s

s t i l l a c o n t r o v e r s i a l s u b j e c t . R e l a t i v e l y few c o m p a r i s o n s o f t h e a c c u r a c y

o f d i f f e r e n t l e n g t h s o f t r i a l s h av e b e e n m ade. H a m i l to n , M i t c h e l l an d

Kamml&de ( d 6 ) u s e d c o l l e c t i o n p e r i o d s o f f i v e o r s i x d a y s an d s t a t e d t h a t

t h e y w ere t o o s h o r t f o r a c c u r a t e r e s u l t s w i t h s t e e r s * S c h n e i d e r and

E l l e n b e r g e r (1 6 2 ) made a s tu d y o f t h e l e n g t h o f s d i g e s t i o n t r i a l on

a p p a r e n t d i g e s t i b i l i t y . They u s e d a t l e a s t a w eek n r e l i m i n a r y p e r i o d and

r a t i o n s t h a t w ore n e a r m a in te n a n c e l e v e l com pared w i t h h i g h e r l e v e l s o f

n u t r i t i o n . They f o u n d t h e g r e a t e s t e r r o r i n c a l c u l a t i n g t h e d i g e s t i o n

c o e f f i c i e n t s was t h e i r r e g u l a r i t y i n t h e q u a n t i t y o f f o c o s e x c r e t e d w h ic h

was more- p ro n o u n c e d a t lovr n u t r i t i o n a l ( m a in te n a n c e } l e v e l s . They fo u n d

t h e d i g e s t i o n c o e f f i c i e n t s f ro m a n i n e - d a y l a c t a t i o n t r i a l ( h i g h p l a n e o f

n u t r i t i o n ) gave a p p r o x i m a t e l y t h e same a c c u r a c y a s r e s u l t s f ro m a t w e n t y -

f o u r - d a y m a in te n a n c e t r i a l , H a m i l to n , M i t c h e l l , K ick end Garmon (3 7 ) u s e d

a t e n - d a y c o l l e c t i o n p e r i o d f o r sh e e p and a f o u r t e e n - d a y c o l l e c t i o n p e r i o d

f o r s t e e r s p r e c e d e d by s e v e r a l w eeks o f p r e l i m i n a r y f e e d i n g . G o t o l a ( 1 7 ° ;

u s e d t e n - d a y c o l l e c t i o n p e r i o d s p r e c e d e d by t e n - d a y p r c l i m i n a r y p e r i o d g

w i t h shee-p on a l f a l f a h a y . F o u r t e o n - d a y r > r o l im in e r y p e r i o d s and f o u r t e m

4

d a y c o l l e c t i o n p e r i o d s w ere u s e d by Mumford e t a l . ( 1 2 7 ) i n d i g e s t i o n

t r i a l s w i t h s t e e r s . K n i g h t , H e p n e r and M o r to n (1 0 5 ) u s e d s e v e n - and

e i g h t - d a y p r e l i m i n a r y p e r i o d s and f i v e - d a y c o l l e c t i o n p e r i o d s w i t h

w e t h e r s . T hese t r i a l s do n o t g iv e much i n f o r m a t i o n o n t h e r e l a t i v e a c ­

c u r a c y o f d i f f e r e n t l e n g t h s o f c o l l e c t i o n ^ p e r i o d s s i n c e t h e t r i a l s a r e

n o t d i r e c t l y c o m p a r a b le .

S t a p l e s and D in u s s o n (1 7 4 ) h a v e r e c e n t l y r e p o r t e d on t h e r e l a t i v e

a c c u r a c y o f s e v e n - an d t e n - d a y c o l l e c t i o n p e r i o d s i n d i g e s t i b i l i t y t r i a l s

w i t h s t e e r s . T hey c a l c u l a t e d c o e f f i c i e n t s o f a p p a r e n t d i g e s t i b i l i t y w i t h

t h e d a t a s e c u r e d f r o m s e v e n - and t e n - d a y c o l l e c t i o n p e r i o d s w i t h 27 i n ­

d i v i d u a l t r i a l s . The d e g r e e o f a c c u r a c y s e c u r e d w i t h a s e v e n - d a y c o l l e c ­

t i o n p e r i o d may be s u f f i c i e n t f o r many s t u d i e s o f a p p a r e n t d i g e s t i b i l i t y

s i n c e t h e y r e p o r t e d t h a t ’•W ith a p o s s i b l e e x c e p t i o n i n t h e c a s e o f

n i t r o g e n - f r e e e x t r a c t t h e s e v e n - d a y c o l l e c t i o n p e r i o d gave c o e f f i c i e n t s

c o m p a ra b le i n a c c u r a c y t o t h e t e n - d a y c o l l e c t i o n p e r i o d " .

C hrom ic O x ide R a t i o T e c h n iq u e

S e v e r a l s t u d i e s h ave b e e n made w i t h d i f f e r e n t s p e c i e s o f a n i m a l s on

th e a d d i t i o n o f known am o u n ts o f c h ro m ic o x id e to t h e r a t i o n and d e t e r ­

m in in g t h e c o n c e n t r a t i o n o f c h ro m ic o x id e i n t h e r e s u l t i n g f e c e s t o a l l o w

t h i s m a t e r i a l t o s e r v e a s a n i n d e x o f d i g e s t i b i l i t y . The u s e o f c h ro m ic

o x id e a s an i n e r t t r a c e r s u b s t a n c e was f i r s t p r o p o s e d by E d in ( 5 9 ) who

f e d chrom ium o x id e im p r e g n a te d i n b l o t t e r p a p e r and r e p o r t e d r e c o v e r i e s

o f 9 9 . 1 p e r c e n t w i t h s l i g h t v a r i a t i o n i n 26 e x p e r i m e n t s . A b r i e f d e s c r i p ­

t i o n o f E d i n ' s c h ro m ic o x id e i n d i c a t o r t e c h n i q u e was p u b l i s h e d i n E n g l i s h

by E d i n , K ih l e n and l l o r d f e l d t ( 6 1 ) . T h is r e p o r t g i v e s r a t h e r c o m p le te

d i s c u s s i o n s o f t h e p r e p a r a t i o n o f t h e c h ro m ic o x id e m a c a r o n i , m i x in g o f

f e e d , c o l l e c t i o n o f f e c e s and t h e d e t e r m i n a t i o n o f chrom ium o x id e i n

f e e d s and f e c e s .

5

H a m i l t o n , M i t c h e l l , K ic k and Garman ( 8 7 ) fo u n d good a g r e e m e n t b e ­

tw e e n t h e c h ro m ic o x id e r a t i o m e th o d and t h e t o t a l f e c a l c o l l e c t i o n

m e th o d w i t h s h e e p , p r o v i d e d t h e c o l l e c t i o n p e r i o d s w ere o f t h r e e d a y s

o r l o n g e r i n d u r a t i o n .

S a t i s f a c t o r y r e s u l t s w i t h t h e c h ro m ic o x id e r a t i o t e c h n i q u e h a v e

b e e n r e p o r t e d m ore r e c e n t l y by A n d e r s e n ( l ) , A n d e rs e n and F r e d e r i l c s e n

( 2 ) , an d S k u lm o w sk i, S zy m a n sk i and 'ifl/yszynski (1 6 6 ) u s i n g sh e e p an d h o r s e s ;

b y B a r n i c o a t (1 9 ) and L lo y d (1 1 2 ) -with s w in e ; by O l s s o n , K i h l e n a n d C a g e l l

( 1 4 2 ) w i t h h o r s e s ; b y K ane , J a c o b s o n a n d Moore ( 1 0 2 ,1 0 3 ) w i t h co w s ; by

S c h u r c h , L lo y d and C ram pton ( 1 6 7 ) w i t h r a t s ; by I r w i n an d C ram pton ( 9 6 ) ,

K r e u l a ( 1 0 8 ) , an d V i r t a n e n ( 1 8 1 ) w i t h h u m a n s ; b y C handa e t a l . ( 3 7 ) w i t h

g o a t s ; and by A x e l s s o n and E r i k s s o n w i t h r u m i n a n t s ( 1 5 ) .

B a r n i c o a t ( 1 9 ) o b t a i n e d c o n s i s t e n t l y lo w d i g e s t i o n c o e f f i c i e n t s w i t h

s h e e p and c a l v e s when t h e c h ro m ic o x id e was g i v e n i n a g e l a t i n c a p s u l e .

They c h e c k e d th e p o s s i b i l i t y o f r e t e n t i o n o f c h ro m ic o x id e i n t h e d i g e s ­

t i v e t r a c t and r e p o r t e d i n c r e a s e d c o n c e n t r a t i o n s i n t h e s to m a c h f o l d s o f

a lamb*

K a n e , J a c o b s o n and Moore ( 1 0 3 ) made a d i r e c t c o m p a r i s o n o f t h e d i ­

g e s t i b i l i t y c o e f f i c i e n t s o b t a i n e d b y u s i n g c h ro m ic o x id e a s an i n d i c a t o r

w i t h t h e t o t a l f e c a l c o l l e c t i o n t e c h n i q u e on s a m p le s r e p r e s e n t i n g t h e

t o t a l c o l l e c t i o n o f f e c e s f ro m cow s. T h i s was done t o e v a l u a t e t h e i n ­

d i c a t o r m ethod a n d t o be a b l e t o e l i m i n a t e t h e e r r o r s due t o s a m p l in g

w h i l e s t u d y i n g t h e e r r o r s due t o t h e m e th o d s b e i n g c o m p a re d . The r e s u l t s

o f t h e i r i n v e s t i g a t i o n showed t h a t t h e r e w e re 110 s i g n i f i c a n t d i f f e r e n c e s

b e tw e e n t h e d i g e s t i o n c o e f f i c i e n t s o b t a i n e d b y t h e t o t a l c o l l e c t i o n

m e th o d and t h o s e s e c u r e d by th e c h ro m ic o x id e r a t i o p r o c e d u r e . R e c o v e r i e s

o f c h ro m ic o x id e w e re r e m a r k a b l y c l o s e t o 100 p e r c e n t .

6

T hey f e d t h e chrom ium o x i d e a s a 15 p e r c e n t m i x t u r e w i t h "wheat f l o u r

b a k e d i n t o a h a r d b r e a d "which w as d r i e d , g ro u n d i n a W i le y M i l l a n d th e n ,

m ix ed w i t h t h e g r a i n i n s u c h a m o u n ts t h a t t h e cows r e c e i v e d a p p r o x i m a t e l y

15 gram s o f c h ro m ic o x id e d a i l y o r 100 gram s o f t h e ch rom ium b r e a d m ix ed

w i t h t h e d a i l y g r a i n r a t i o n .

C o m p a r is o n s o f v a r i o u s m e th o d s o f f e e d i n g may s e r v e t o e m p h a s iz e

t h e i m p o r t a n c e o f t h i s p h a s e o f t h e ’’R a t i o ” p r o c e d u r e s p a r t i c u l a r l y w i t h

t h e u s e o f c h ro m ic o x i d e .

V a r i a b l e r e c o v e r i e s o f c h ro m ic o x id e f r o m s h e e p -were s e c u r e d b y

C ram pton an d L lo y d ( 4 5 ) w i t h d i f f e r e n t m e th o d s o f a d m i n i s t r a t i o n o f t h e

c h ro m ic o x i d e , b u t t h e i r r e s u l t s i n d i c a t e d t h a t t h e c h ro m ic o x id e may be

a c c u r a t e l y u s e d i n d e t e r m i n i n g t h e d i g e s t i b i l i t y o f a sh e e p r a t i o n , p r o ­

v i d e d t h e c h ro m ic o x id e c a n be p r e m ix e d w i t h g round g r a i n i n t h e r a t i o n ,

b u t n o t w hen i t i s g i v e n s e p a r a t e l y a s was n e c e s s a r y o n a n e n t i r e l y

ro u g h a g e r a t i o n . T h is i s shown i n t h e f o l l o w i n g t a b l e f r o m C ram p to n and

L lo y d ( 4 5 ) w here t h e c h ro m ic o x i d e o n t h e ro u g h a g e a l o n e r a t i o n w as f e d

a s a c o n c e n t r a t e d p e l l e t ( s h e e p l a n d 2) and on t h e ro u g h a g e p l u s g r a i n

r a t i o n t h e c h ro m ic o x i d e was m ix ed w i t h t h e g r a i n ( s h e e p 5 and 4 ) .

T a b le 1

R e c o v e ry o f C hrom ic Oxide"*'

S h eep R a t i o n R e c o v e ry (%)

1 Roughage + chrom ium p e l l e t s 85

2 R oughage + chrom ium p e l l e t s 87

3 R oughage + g r a i n + chrom ium 98

4 R oughage + g r a i n + chrom ium 99

^■From C ram pton a n d L lo y d ( 4 5 ) .

7

T h is may p a r t i a l l y e x p l a i n t h e lo w d i g e s t i b i l i t y c o e f f i c i e n t s o b t a i n e d

b y B a r n i c o a t ( 1 9 ) w i t h s h e e p and c a l v e s when t h e c h ro m ic o x id e w as g i v e n i n

a g e l a t i n c a p s u l e w h ic h w ou ld be c o m p a ra b le t o t h e p e l l e t e d c h ro m ic o x i d e

c o n c e n t r a t e f e e d i n g r e p o r t e d by C ram p to n and L lo y d (4 5 )* Tho ro u g h a g e p l u s

g r a i n p l u s chrom ium r e p o r t e d b y C ram pton and L lo y d (4 5 ) w o u ld be c o m p a ra b le

t o t h e m e th o d o f f e e d i n g em ployed by Kane e t a l . (1 0 3 ) w i t h cows w h ic h a l s o

gave s a t i s f a c t o r y r e s u l t s ,

J a r l ( 9 9 ) f e l t t h a t t h e c h ro m ic o x id e i n d i c a t o r m ethod w as s u p e r i o r

t o t h e t o t a l f e c a l c o l l e c t i o n m e th o d s i n c e i t i s n o t i n f l u e n c e d a s g r e a t l y

b y v a r i a t i o n s i n t h e d a i l y am ount o f f e c e s v o i d e d . He s t a t e d t h a t ’’A b o u t

t h e same m e t h o d o l o g i c a l a c c u r a c y i s a c h i e v e d i n s i x r e p e a t e d e x p e r i m e n t s

(7 2 c o l l e c t i o n d a y s ) w i t h t h e ’ q u a n t i t a t i v e * m ethod a s i n one e x p e r i m e n t

c o n d u c te d a c c o r d i n g t o t h e i n d i c a t o r m e th o d ” . He f e l t t h a t t h e r e w as a

c o n s t a n t r e l a t i o n b e tw e e n t h e c h ro m ic o x id e and t h e v a r i o u s n u t r i e n t s i n

t h e r a t i o n a n d f e c e s , so t h a t a v a r i a t i o n i n f e c e s q u a n t i t y on two s u c ­

c e s s i v e d a y s w o u ld n o t a f f e c t t h e c a l c u l a t e d d i g e s t i b i l i t i e s . R e c e n t

d a t a o f K a n e , J a c o b s o n a n d Moore (1 0 4 ) showed a v a r i a t i o n i n t h e c o n c e n ­

t r a t i o n o f c h ro m ic o x id e i n i n d i v i d u a l p a s s a g e s o f f e c e s t h r o u g h o u t a 2 4 -

h o u r p e r i o d w h ic h d o es n o t a g r e e w i t h J a r l ’ s ( 9 9 ) a s s u m p t i o n t h a t t h e r e

was a c o n s t a n t r e l a t i o n b e tw e e n th e c h ro m ic o x i d e an d t h e v a r i o u s co n ­

s t i t u e n t s i n t h e f e c e s .

A n d e r s e n and W in th e r ( 3 ) fo u n d t h a t a p r e l i m i n a r y p e r i o d o f e i g h t o r

n i n e d a y s was s u f f i c i e n t f o r r e p r e s e n t a t i v e s a m p le s when u s i n g t h e c h ro m ic

o x i d e r a t i o m e th o d . They made a q u a n t i t a t i v e f e c e s c o l l e c t i o n f ro m f o u r

i n d i v i d u a l cows d u r i n g 20 d a y s w h i l e t h e y r e c e i v e d a c o n s t a n t am oun t o f

f e e d c o n t a i n i n g 1 4 .8 2 gram s o f c h ro m ic o x i d e . The a v e r a g e e x c r e t i o n p e r

d a y w as c a l c u l a t e d t o be 1 4 .6 1 gram s o f ch ro m ic o x id e w h ich i s 9 8 . 6 p e r ­

c e n t o f t h e am o u n t consum ed . S in c e t h e y fo u n d t h e r e c o v e r y o f chrom ium

8

*to be a lw a y s lo w "they p r o p o s e d a c o r r e c t i o n by r a i s i n g "the am ount o r

chrom ium fo u n d b y two p e r c e n t o f t h e v a l u e . T hey p r e s e n t e d t a b l e s w h ic h

showed t h a t t h e c h ro m ic o x id e i n d i c a t o r m e thod gave t h e same c o e f f i c i e n t s

o f d i g e s t i b i l i t y a s t h e t o t a l f e c a l c o l l e c t i o n m e th o d . T h ey a l s o c o n ­

d u c t e d t h r e e e x p e r i m e n t s w i t h n i n e cows i n w h ic h t h e y a n a l y z e d t h e f e c e s

f ro m e a c h cow t h a t was e x c r e t e d d u r i n g t h e d a y and t h e n t h e f e c e s t h a t

w e re e x c r e t e d d u r i n g t h e f o l l o w i n g n i g h t . They fo u n d t h e r a t i o s o f

c h ro m ic o x i d e t o t h e v a r i o u s n u t r i e n t s i n t h e f e c e s v a r i e d b e tw e e n d a y

and n i g h t f e c e s * b u t w ere n o t a lw a y s h i g h e r f o r one t h a n t h e o t h e r an d

s u g g e s t e d t h a t t h e p a r t i a l c o l l e c t i o n o f f e c e s s a m p le s be done t h r o u g h o u t

t h e e n t i r e 2 4 -h o u r d a y .

Chanda* Clapham* M chaught and Owen ( 3 7 ) u s e d t h e c h ro m ic o x id e r a t i o

t e c h n i q u e t o s tu d y t h e d i g e s t i b i l i t y o f c a r o t e n e b y cows and g o a t s f e d

d r i e d g r a s s . W i th g o a t s t h e t o t a l f e c a l c o l l e c t i o n t e c h n i q u e was com pared

w i t h t h e chrom ium r a t i o t e c h n i q u e . When m ix ed w i t h t h e c o n c e n t r a t e p o r ­

t i o n o f t h e r a t i o n o f l a c t a t i n g g o a t s * 10 0 .0 * 9 9 . 1 , 9 9 .1 and 9 6 .0 p e r c e n t

o f t h e c h ro m ic o x id e f e d was r e c o v e r e d i n t h e f e c e s i n f o u r e x p e r i m e n t s

w i t h f o u r d i f f e r e n t g o a t s . The a p p a r e n t d i g e s t i b i l i t y o f c a r o t e n e by t h e

g o a t w as d e t e r m in e d b y t o t a l c o l l e c t i o n i n m e ta b o l i s m c r a t e s and a l s o by

t h e chrom ium r a t i o t e c h n i q u e . By t h e t o t a l c o l l e c t i o n t e c h n i q u e t h e d i ­

g e s t i b i l i t i e s o f c a r o t e n e i n f o u r g o a t s w e re 6 8 . 7 , 6 2 .7 * 6 1 .8 and 5 9 .6

p e r c e n t . The c o r r e s p o n d i n g d i g e s t i b i l i t i e s o b t a i n e d f ro m t h e same f e c e s

s a m p le s b y t h e c h ro m ic o x id e r a t i o m e th o d w ere 6 7 . 4 , 6 2 .9 * 6 1 .8 an d 5 8 .9

p e r c e n t .

E r i k s s o n ( 6 3 ) com pared t h e d i g e s t i o n c o e f f i c i e n t s o b t a i n e d by t h e

t o t a l f e c a l c o l l e c t i o n m e th o d i n d i f f e r e n c e t r i a l s w i t h w e t h e r s w i t h t h o s e

c a l c u l a t e d f o r cows by t h e ch rom ium r a t i o t e c h n i q u e and c o n c lu d e d t h a t t h e

t o t a l c o l l e c t i o n m e th o d gave t h e m o s t r e l i a b l e r e s u l t s .

E d i n (6 0 ) r e p o r t e d t h a t t h e chrom ium r a t i o m e th o d o f c a l c u l a t i n g t h e

d i g e s t i o n c o e f f i c i e n t s o f f e e d s when u s i n g a. tw o d ay c o l l e c t i o n p e r i o d

gave a s a c c u r a t e c o e f f i c i e n t s a s t h e t o t a l c o l l e c t i o n m ethod i n a s e v e n

t o e i g h t d a y p e r i o d . A x e l s s o n en d K iv im ae ( 1 7 ) c a l c u l a t e d d i g e s t i o n c o ­

e f f i c i e n t s by t h e chrom ium r a t i o p r o c e d u r e and f ro m t h e n u t r i e n t consum p-

t i o n - e x c r o t i o n r a t i o s on t h e same sa m p le s c o l l e c t e d a t two day i n t e r v a l s

f ro m t h r e e w e t h e r s o v e r a p e r i o d o f 44 d a y s . The a v e r a g e d i g e s t i o n co ­

e f f i c i e n t s o f t h e 22 p e r i o d s w ere n e a r l y t h e same f o r t h e two m e th o d s o f

c a l c u l a t i o n . The d i g e s t i o n c o e f f i c i e n t s c a l c u l a t e d by t h e t o t a l c o l l e c t i o n

and t h e chrom ium r a t i o t e c h n i q u e s r e s p e c t i v e l y w e r e ; o r g a n i c m a t t e r 7 1 .7

and 7 1 . 2 ; p r o t e i n * 7 4 .5 a n d 7 4 . 2 ; 'Other e x t r a c t * 7 0 .1 an d 3 9 . 3 ; n i t r o g e n -

f r e e e x t r a c t * 7 7 . 2 and 7 6 . 8 ; a n d c r u d e f i b e r * 5 3 .7 a n d 5 2 . 9 . They f u r t h e r

showed t h a t t h e a v e r a g e d i g e s t i o n c o e f f i c i e n t was i n d e p e n d e n t o f t h e

l e n g t h o f t h e c o l l e c t i o n p e r i o d (tw o t o t e n d a y s ) b u t t h a t t h e s t a n d a r d

d e v i a t i o n d e c r e a s e d r a p i d l y w i t h i n c r e a s e d l e n g t h o f t h e p e r i o d .

L i g n i n R a t i o T e c h n iq u e

L i g n i n h a s b e e n q u i t e w i d e l y s t u d i e d d u r i n g t h e p a s t f e w y e a r s s in c e *

i f i t c o u l d be e s t a b l i s h e d t h a t i t i s a n i n d i g e s t i b l e s u b s t a n c e * i t w ou ld

a l s o m e e t t h e r e q u i r e m e n t s o f b e i n g a n a t u r a l c o n s t i t u e n t o f t h e p l a n t

m a t e r i a l .

L i g n i n h a s b e e n r e p o r t e d t o be i n d i g e s t i b l e by s t e e r s ( 4 6 ) ; b y cows

on a m ix ed f e e d and b y sh e e p on d r i e d Sudan g r a s s ( 6 2 ) ; b y cows on a l ­

f a l f a h a y ( 8 4 ) ; b y s h e e p ( 8 3 ) ; by s h e e p 011 m ixed f e e d s ( 1 7 8 ) ; b y sh e e p

o n K o re a n l e s p e d e z a h a y c u t a t f o u r s t a g e s o f m a t u r i t y ( 4 1 ) ; by s t e e r s

on p a s t u r e f o r a g e ( 6 9 ) ; by cows on a r a t i o n o f a l f a l f a s i l a g e , c o r n s i l a g e

an d g r a i n , and a l s o on a r a t i o n o f a l f a l f a hay* c o r n s i l a g e and g r a i n

( 1 0 3 ) ; and by cows f e d w h e a t s t r a w ( 6 6 ) .

10

S w i f t e^t &1. ( 1 7 8 ) h ad 16 t r i a l s u s i n g sh e e p on m ixed r a t i o n s and

c o m p ared th© d i g e s t i b i l i t y c o e f f i c i e n t s c a l c u l a t e d b y t h e l i g n i n r a t i o

m e th o d w i t h t h e c o n v e n t i o n a l t o t a l c o l l e c t i o n m e th o d and. fo u n d t h e two t o

c h e c k v e r y c l o s e l y and s t a n d a r d e r r o r s o f t h e d i g e s t i o n c o e f f i c i e n t s d e ­

t e r m i n e d by t h e tw o m e th o d s w e re o f t h e same g e n e r a l . m a g n i t u d e .

F o r b e s and G -a r r ig u s (7 0 ) u s e d t h e l i g n i n r a t i o t e c h n i q u e t o s tu d y t h e

d i g e s t i b i l i t y o f p a s t u r e f o r a g e s by s t e e r s and w e t h e r s . The a v e r a g e r e ­

c o v e r y o f l i g n i n i n s e v e n d i g e s t i o n t r i a l s w i t h s t e e r s was 102 + 7 p e r c e n t .

C o m p a r is o n s o f t h e d r y m a t t e r i n t a k e s and t h e d i g e s t i b i l i t y c o e f f i c i e n t s

o f t h e d r y m a t t e r a s c a l c u l a t e d b y t h e l i g n i n r a t i o m ethod and t h e p l a n t

p ig m e n t r a t i o showed e x t r e m e v a r i a t i o n s i n t h e s t u d y r e p o r t e d by Cook and

H a r r i s ( 4 0 ) . F o ra g e c o n s u m p t io n a s d e t e r m i n e d by t h e l i g n i n r a t i o t e c h ­

n iq u e h o w e v e r , a g r e e d c l o s e l y w i t h t h e c a l c u l a t e d d r y m a t t e r i n t a k e s

commonly a c c e p t e d f o r t h e v a r i o u s s i z e s o f s h e e p . I n a d d i t i o n , t h e c a l ­

c u l a t e d d i g e s t i b i l i t y o f t h e d r y m a t t e r by t h e u s e o f t h e l i g n i n r a t i o

t e c h n i q u e com pared f a v o r a b l y w i t h t h e r e s u l t s o b t a i n e d by* o t h e r i n v e s t i ­

g a t o r s on s i m i l a r f o r a g e s . T h i s was n o t t r u e w i t h a l l s p e c i e s s t u d i e d

f o r c a l c u l a t i o n s raa.de by t h e p l a n t p ig m e n t r a t i o t e c h n i q u e .

f i l l i s , M a tro n s arid M aynard (6 2 ) d e t e r m i n e d d i g e s t i b i l i t y c o e f f i c i e n t s

b y t h e c o n v e n t i o n a l t o t a l f e c a l c o l l e c t i o n te c } m iq u o an d a l s o by t h e l i g n i n

r a t i o t e c h n i q u e u s i n g v a r i o u s r a t i o n s w i t h cow s, r a b b i t s and sheet)* They

s e c u r e d v e r y c l o s e c h e c k s b e tw e e n t h e two m e th o d s f o r d i g e s t i b i l i t y o f t h e

d r y m a t t e r and t h e o t h e r f e e d c o n s t i t u e n t s . They f u r t h e r showed v e r y

s m a l l d a i l y v a r i a t i o n s i n t h o l i g n i n c o n t e n t o f f e c e s f rom t h r e e six cep

f e d t i m o t h y h a y , w h ic h w o u ld make t h e s h o r t e n e d c o l l e c t i o n p e r i o d o f t h e

p a r t i a l f e c a l c o l l e c t i o n t e c l n i i q u e sat?, s f a c t o r y .

H a l o , D u n can and H uffm an (8 4 ) p r o p o s e d t h a t l i g n i n be u s e d a s an

i n d i c a t o r f o r t h e s t u d v o f d i g e s t i b i l i t y i n th o rum en s i n c e l i g n i n d i d

11

not: a p p e a r t o be a p p r e c i a b l y d i g e s t e d i n t h e rum en ev en t h r o u g h t o t a l

d i g e s t i o n r a n g e d u p t o 2 3 .7 p e r c e n t * D i g e s t i b i l i t y o f l i g n i n r a n g i n g

f ro m n e g a t i v e v a l u e s t o 29 p e r c e n t 'were r e p o r t e d by F o r b e s and S w i f t

( 7 2 ) .

F o r b e s an d G a r r i g u s (70^) r e p o r t e d a t o t a l o f 70 g r a z i n g t r i a l s w i t h

s t e e r s an d w e t h e r s u s i n g t h e l i g n i n r a t i o t e c h n i q u e and c o n d u c te d p e r i o d i c

t r i a l s i n d i g e s t i o n s t a l l s u s i n g c u t f o r a g e and t o t a l f e c a l c o l l e c t i o n s

t o c o n f i r m t h e r e l i a b i l i t y o f t h e l i g n i n r a t i o t e c h n i q u e . The a v e r a g e

r e c o v e r y o f l i g n i n f ro m s t e e r s f e d i n t h e d i g e s t i o n s t a l l s w as 106 + 5 .8

p e r c e n t , a n d f ro m lam b s t h e a v e r a g e r e c o v e r y was 111 + 8 , 7 p e r c e n t . T hey

d i d n o t p r e s e n t d a t a , b u t s t a t e d t h a t t h e y i n v e s t i g a t e d t h e m e th o x y l c o n ­

t e n t o f t h e f o r a g e l i g n i n an d t h e f c c e s l i g n i n b u t c o u ld n o t a c c o u n t f o r

t h e s l i g h t l y h i g h r e c o v e r i e s . A c t u a l c o m p a r i s o n s o f t h e d i g e s t i b i l i t y

c o e f f i c i e n t s o b t a i n e d by th e c o n v e n t i o n a l m e th o d and t h e l i g n i n r a t i o

m e th o d a r e made i n a l a t e r p a p e r by F o r b e s and G a r r i g u s (7 1 ) a n d v e r y

good a g r e e m e n t b e tw e e n t h e two m e th o d s a r e e v i d e n t . D i g e s t i o n c o e f f i c i e n t s

o b t a i n e d f o r l i g p i n by t h e t o t a l c o l l e c t i o n t e c h n i q u e w ere lo w e x c e p t f o r

h i g h n e g a t i v e c o e f f i c i e n t s i n f o u r t r i a l s w i t h w e t h e r s b ed d ed w i t h wood

s h a v i n g s .

M a r s h a l l (1 1 6 ) u s e d t h e l i g n i n r a t i o m ethod t o s t u d y t h e d i g e s t i b i l i t y

o f p e n t o s a n s o f h a y i n v a r i o u s a r e a s o f t h e d i g e s t i v e t r a c t o f two s h e e p .

V a r i o u s d e g r e e s o f d i g e s t i o n o f l i g n i n h a v e b e e n r e p o r t e d by v a r i o u s

w o r k e r s , b u t c o m p a r i s o n s b e tw e e n d i f f e r e n t e x p e r i m e n t s a r c d i f f i c u l t t o

e v a l u a t e s i n c e d i f f e r e n t a n a l y t i c a l m e th o d s and d i f f e r e n t a n im a l s p e c i e s

w e re u s e d .

C ram pton and M aynard ( 4 6 ) r e p o r t e d l i g n i n to be a s h i g h a s 30 p e r c e n t

o r m ore d i g e s t i b l e i n f e e d b a r l e y , w h e a t s c r e e n i n g s and f e e d o a t s when

d e t e r m in e d by t h e i r m e th o d , b u t was a l m o s t c o m p l e t e l y i n d i g e s t i b l e w hen

d e t e r m i n e d ’’b y d i f f e r e n c e a s p r o p o s e d by C ram p to n an d W h i t in g ( 4 7 ) .

E v id e n c e t h a t some c h a n g e may o c c u r i n l i g n i n a s i t p a s s e d t h r o u g h

t h e d i g e s t i v e t r a c t o f r u m i n a n t s h a s b e e n p r e s e n t e d by s e v e r a l i n v e s t i g a ­

t o r s . C so n k a , P h i l l i p s and J o n e s (4 8 ) r e p o r te d , a d e c re a .s e i n m e th o x y l

g r o u p s o f l i g n i n t h a t h a d b e e n t h r o u g h t h e r u m in a n t d i g e s t i v e t r a c t .I

P a ^ u r a n d DeLong (1 4 5 ) fo u n d an i n c r e a s e d e x c r e t i o n o f b e n z o i c and

h i p p u r i c a c i d s i n t h e u r i n e o f sh e e p f e d i n c r e a s e d am o u n ts o f l i g n i n .

The i n c r e a s e d u r i n a r y c o n c e n t r a t i o n o f a r o m a t i c a c i d s w ere b e l i e v e d t o be

e x c r e t o r y p r o d u c t s o f t h e a r o m a t i c r i n g s f ro m t h e d e g r a d a t i o n o f l i g n i n .

L i g n i n i s o l a t e d f ro m f o r a g e s y i e l d e d up t o 20 p e r c e n t o f i t s w e i g h t a s

a l d e h y d e s when t r e a t e d w i t h n i t r o b e n z e n e i n a l k a l i , b u t l i g n i n i s o l a t e d

f r o m f e c e s y i e l d e d no a l d e h y d e s when c o rn u a ra b ly t i ' e a t e d i n e x p e r i m e n t s o f

B ond i an d Meyer ( 2 8 ) . They a l s o fo u n d a s l i g h t i n c r e a s e i n n i t r o g e n c o n ­

t e n t , b u t no c h a n g e i n t h e m e th o x y l c o n t e n t o f l i g n i n i s o l a t e d f ro m f e c c s

a s com pared t o t h a t i s o l a t e d f ro m f o r a g e s . F o rb e s and G a r r i g u s (7 1 ) fo u n d

no ch an g e i n t h e m e th o x y l c o n t e n t o f f o r a g e l i g n i n i n t h e d i g e s t i v e t r a c t

o f s h e e p .

p a lo h e im o ( 1 4 s , 144) and P h i l l i p s (1 4 6 ) h a v e d e t e r m i n e d t h e n i t r o g e n

c o n t e n t o f c r u d e l i g n i n an d d e d u c t e d f ro m th e c ru d e l i g n i n p e r c e n t a g e on

t h e a s s u m p t i o n t h a t t h e n i t r o g e n o u s r e s i d u e i s a p r o t e i n . The p r i n c i p a l

d i f f i c u l t y i n o b t a i n i n g r e l i a b l e f i g u r e s f o r l i g n i n i n p r o t e i n - r i c h ma­

t e r i a l s i s t h e r e m o v a l o f t h e p r o t e i n w i t h o u t re m o v in g a. p a r t o f t h e l i g n i n .

H o m a n and J e n k i n s ( 1 3 9 ) f e l t t h a t a g r e a t e r e r r o r m ig h t be made i n c a l ­

c u l a t i n g t h i s n i t r o g e n a s p r o t e i n t h a n by n o t c o r r e c t i n g a t a l l . The f a c t

t h a t no one had e v e r s u c c e e d e d i n i s o l a t i n g a n i t r o g e n - f r e e l i g n i n p r e ­

p a r a t i o n f ro m s u c c u l e n t p l a n t t i s s u e l e d M acD o u g a ll and DeLong ( 1 1 4 ) t o

13

g iv e s t r o n g c o n s i d e r a t i o n t o t h e p o s s i b i l i t y t h a t n i t r o g e n i s a f u n d a ­

m e n ta l c o m p o n en t o f t h e l i g n i n o f s u c c u l e n t p l a n t m a t e r i a l s . B ond i and

M eyer ( 2 8 ) p r e p a r e d l i g n i n s f r o m a num ber o f a n n u a l g r a s s e s and le g u m e s

by e x t r a c t i o n w i t h d i l u t e a l k a l i . The p r e p a r a t i o n s c o n t a i n e d n i t r o g e n

w h ic h t h e y f e l t w as n o t due to c o n t a m i n a t i o n w i t h p r o t e i n s , b u t seem ed t o

be a c h a r a c t e r i s t i c com ponen t o f t h e l i g n i n m o le c u le i t s e l f . They b e l i e v e d

t h a t t h e c o n s t a n c y o f t h e n i t r o g e n c o n t e n t o f t h e i r l i g n i n p r e p a r a t i o n s

f ro m t h e same p l a n t m a t e r i a l i n c o n s e c u t i v e e x t r a c t i o n s s u p p o r t e d t h e i r

o p i n i o n . They a l s o rem oved m o s t o f t h e p r o t e i n f ro m t h e p l a n t m a t e r i a l

by t r e a t m e n t w i t h v e r y d i l u t e so d iu m h y d r o x id e o r by t h e a c t i o n o f p e p s i n

i n d i l u t e h y d r o c h l o r i c a c i d b e f o r e e x t r a c t i n g t h e l i g n i n and f o u n d t h a t

t h e l i g n i n f ro m p l a n t s g iv e n t h e s e p r o l i m i n a r y t r e a t m e n t s showed a p p r o x i ­

m a t e l y t h e same n i t r o g e n c o n t e n t a s t h a t f ro m p l a n t m a t e r i a l w h ic h d i d n o t

r e c e i v e i t . De Man and De Heus (5 2 ) h y d r o l y z e d l i g n i n p r e p a r a t i o n s f ro m

a sam ple o f L o l iu m p e r e n n e w i t h s t r o n g so d iu m h y d r o x id e and d e t e r m i n e d

t h e t y r o s i n e an d t r y p t o p h a n e c o n t e n t s and a l s o c a l c u l a t e d t h e t y r o s i n e -

n i t r o g e n and t r y p t o p h a n e - n i t r o g e n a s p e r c e n t a g e o f t h e t o t a l n i t r o g e n i n

t h e s e p r e p a r a t i o n s and com pared t h e s e f i g u r e s w i t h t h e c o m p o s i t i o n o f t h e

t r u e p r o t e i n o f t h e g r a s s . Tho t y r o s i n e - n i t r o g e n c a l c u l a t e d a s p e r c e n t a g e

o f t h e t o t a l n i t r o g e n o f th o p r e p a r a t i o n s c o r r e s p o n d e d c l o s e l y w i t h t h e

f i g u r e f o r t h e t r u e p r o t e i n o f L o l iu m p e r e n n e . The c o r r e s p o n d i n g f i g u r e s

f o r t r y p t o p h a n e c h e c k e d o n l y i n t h e c a s e o f l i g n i n p r e p a r e d a c c o r d i n g t o

t h e m e th o d o f Bondi and M eyer ( 2 8 ) w h ic h u s e s no s t r o n g a c i d t o d e s t r o y

t r y p t o p h a n e . T hese r e s u l t s l e n d s u p p o r t t o t h e c a l c u l a t i o n o f p r o t e i n

e q u i v a l e n t f ro m t h e n i t r o g e n r e s i d u e s i n th e l i g n i n . Thomas and A rm s t ro n g

( 1 7 9 ) c o m p ared t h e Horman and J e n k i n s ( 1 3 9 ) , the- C ram pton and M aynard ( 4 6 ) ,

an d t h e E l l i s , Matron© a rd M aynard (6 2 ) m e th o d s o f d e t e r m i n i n g l i g n i n a l l

o f w h ic h i n v o l v e t h e u s e o f ,72 p e r c e n t s u l f u r i c a c i d . The l i g n i n y i e l d s

o b t a i n e d w i t h t h e m e th o d o f E l l i s , M a tro n e an d M aynard w ere a p p r e c i a b l y

h i g h e r t h a n t h o s e o f t h e m e thod o f Horman an d J e n k i n s . bhen a p r o t e i n

c o r r e c t i o n f a c t o r was u s e d t h e r e s u l t s o f t h e tw o m e th o d s w e re com pe.rs .b le .

Thomas an d A rm s tro n g (1 7 9 ) f u r t h e r showed t h a t a c i d h y d r o l y s a t e s f ro m

c r u d e l i g n i n i s o l a t e d f ro m p l a n t m a t e r i a l and f ro m f e c e s c o n t a i n e d am ino -

a c i d s .

I n d i g e s t i b l e P r o t e i n R a t i o T e c h n iq u e

S e v e r a l a p p r o a c h e s h a v e b e e n made t o t h e u s e o f f o r a g e o r f e c e s p r o ­

t e i n , o r a c o m b i n a t i o n o f t h e s e , f o r t h e c a l c u l a t i o n o f f o r a g e d i g e s t i b i l ­

i t y . The p r i n c i p a l a d v a n t a g e o f t h i s t e c h n i q u e f o r p a s t u r e d i g e s t i b i l i t y

s t u d i e s i s t h a t i t e l i m i n a t e s a l a r g e p a r t o f t h e p a s t u r e s a m p l in g e r r o r .

S in c e g r a z e d f o r a g e i s e x t r e m e l y d i f f i c u l t t o sam ple t h a t w h ic h i s r e p r e ­

s e n t a t i v e o f t h e f o r a g e g r a z e d b y th e a n i m a l , some e r r o r i s p e r m i s s a b l e

i n t h e c a l c u l a t i o n o f f e e d i n t a k e o r d i g e s t i b i l i t y o f p a s t u r e b y t h e n i t r o ­

gen c o n t e n t an d s t i l l s e c u r e g r e a t e r a c c u r a c y t h a n may be a t t a i n e d by

a t t e m p t s t o sam p le t h e g r a z e d f o r a g e .

G a l lu p and B r i g g s (7 8 ) b e l i e v e d t h a t a c o n s t a n t r e l a t i o n s h i p e x i s t e d

b e tw e e n t h e am oun t o f f e c a l n i t r o g e n and t h e d r y m a t t e r i n t a k e , r e g a r d l e s s

o f t h e am ount o f p r o t e i n i n t h e f o r a g e . B o th F o rb e s \ ,6 7 ) and B l a x t e r and

M i t c h e l l ( 2 6 ) h av e p r e s e n t e d d a t a t o show t h a t a c o n s t a n t r e l a t i o n s h i p d o e s

n o t h o l d . F o r b e s (6 7 ) fo u n d t h a t t h e d a t a f o r f r e s h g r a s s i n d i c a t e d t h a t

t h e t o t a l f e c a l n i t r o g e n v a r i e d to o w i d e l y to be u s e d a s s u g g e s t e d by

G a l l u p and B r ig g s ( 7 8 ) . He a l s o found t h a t w i t h d r i e d ro u g h a g e s t h e r e

7/ a s a s t e a d y r i s e i n f e c a l n i t r o g e n e x c r e t i o n p e r 100 grams o f d r y m a t t e r

i n t a k e a s t h e p e r c e n t a g e o f p r o t e i n i n t h e ro u g h a g e i n c r e a s e d . L a n c a s t e r

( 1 1 1 ) p r o p o s e d a m ethod f o r t h e c a l c u l a t i o n o f o r g a n i c l e t t e r d i g e s t i b i l i t y

17

H eller , Breed lev 1© and L ikely (90) used the normal iron content o f a

ra tio n as the in d ica to r substance fo r determining the d ig e s t ib i l i t y o f

ra tio n s fo r rate*

S i l i c a Ratio Technique

The s i l i c a r a tio technique fo r the determ ination o f d ig e s t ib i l i t y

o f feed s has u t i l iz e d both the natu ra lly -con ta in ed s i l i c a and a lso

added amounts o f s i l ic a *

Gallup (77) used the s i l i c a r a tio technique w ith ra ts on a d ie t con­

ta in in g one percent o f added s i l i c a and secured r e su lts which checked

c lo s e ly w ith those obtained by standard methods* Gallup and Kuhlman (80)

used cows on a r a tio n which contained approximately three percent o f

n atu ra lly -occu rrin g s i l i c a and 0*5 percent o f added iron oxide and secured

r e s u lts which in d ica ted th a t the s i l i c a n a tu ra lly contained in the feed

was superior to iron oxide as an in d ica tor substance in d ig e stio n t r ia ls *

A la te r t r i a l w ith mung bean s ila g e was conducted by Gallup and Kuhlman

(8 1 ) . This mung bean s ila g e contained approximately 20 percent o f s i l i c a

which was more than s ix tim es the concentration p rev iou sly used. They

found th e s i l i c a r a tio technique u n sa tisfa c to ry because the r a tio o f food

c o n stitu e n t to s i l i c a r a tio o f the feed varied from day to day. The r a tio

o f fe c e s co n stitu en ts to s i l i c a content showed such wide v a r ia tio n s during

a 24-hour period th a t random sampling o f the fe c e s was not j u s t i f ia b le .

While they did not determine the cause o f these v a r ia t io n s , they p ostu la ted

th a t they could be due to an uneven d is tr ib u tio n o f the s i l i c a in the feed

and a lso to s t r a t i f ic a t io n and lo s s o f s i l i c a in i t s passage through the

in te s t in a l t r a c t . G allup, Hobbs and Briggs (79) made a study o f a s e r ie s

o f ra tio n s using s te e r s and sheep fo r comparison of the s i l i c a r a tio tech ­

nique w ith th e standard method and for c a lc u la tio n of s i l i c a recovery. The

recovery o f in gested s i l i c a was p r a c t ic a lly q u an tita tive when the s te e r s

were in stanchions and the f e c e s c o lle c te d semimanually. 'When the s te er s

18

w e re I n d r y l o t and th@ f e c e s c o l l e c t e d i n c a n v a s s a c k s , t h e a v e r a g e e x ­

c r e t i o n o f f e c a l s i l i c a e x c e e d e d t h e c a l c u l a t e d i n t a k e b y a b o u t l u p e r c e n t ,

Yfhen t h e s t e e r s w e re on p a s t u r e , f e c a l s i l i c a e x c r e t i o n w as 66 p e r c e n t

h i g h e r t h a n t h e c a l c u l a t e d i n t a k e , p r o b a b l y d u e t o t h e i n g e s t i o n o f d i r t

by t h e g r a z i n g a n i m a l s . I n t h e s h e e p t r i a l s I n m e ta b o l i s m c r a t e s , f e c a l

s i l i c a c o n t e n t a v e r a g e d 107 p e r c e n t o f t h e c a l c u l a t e d i n t a k e . T hey f e l t

t h a t c o n t a m i n a t i o n o c c u r r e d when t h e f e c e s w ere e x p o s e d t o b a r n d u s t d u r i n g

t h e d a y o f c o l l e c t i o n s . T h e i r r e s u l t s i n d i c a t e t h a t t h e s i l i c a r a t i o t e c h ­

n iq u e i s a d a p t a b l e t o d i g e s t i o n t r i a l s w i t h s t e e r s an d s h e e p i f t h e r e ­

c o v e r y o f s i l i c a i s r e a s o n a b l y c l o s e t o 100 p e r c e n t . E x t r a p r e c a u t i o n s

a r e a p p a r e n t l y n e c e s s a r y i n u s i n g t h e s i l i c a r a t i o t e c h n i q u e t o k e e p co n ­

t a m i n a t i o n o f t h e sam p le a t a minimum. D ruce and iY il lc o x (5 6 ) s e c u r e d

good r e c o v e r y o f n a t u r a l f e e d s i l i c a f ro m t h e f e c a l m a t e r i a l o f r a b b i t s

and t h u s t h e s i l i c a r a t i o t e c h n i q u e gave r e s u l t s c o m p a ra b le w i t h t h e co n ­

v e n t i o n a l t o t a l eo 3 .1 © ctio n m ethod* They w e re aw are o f c e r t a i n o b j e c t i o n s

t o t h e s i l i c a r a t i o m e th o d , s u c h a s t h e v a r i a t i o n i n t h e r e c o v e r y v a l u e s

b e tw e e n i n d i v i d u a l a n i m a l s and t h e p o s s i b i l i t y ? - o f s i l i c a c o n t a m i n a t i o n

f r o m t h e s o i l i n p a s t u r e s t u d i e s .

P l a n t P ig m e n t R a t i o T e c h n iq u e

The u s e o f a n a t u r a l l y - o c c u r r i n g p l a n t p ig m e n t o r g ro u p o f p ig m e n ts

w h ic h a r e f u l l y r e c o v e r a b l e i n t h e f e c e s h a s t h e same a d v a n ta g e a s o t h e r

n a t u r a l l y - o c c u r r i n g f e e d c o n s t i t u e n t s i n t h a t , i n a d d i t i o n t o d e t e r m i n i n g

t h e d i g e s t i b i l i t y o f t h e f e e d s t u d i e d , t h e y w i l l a l s o p e r m i t a n I n d i r e c t

m e a s u re m e n t o f t h e q u a n t i t y o f p a s t u r e h e rb a g e consum ed by e r a s i n g a n i m a l s .

The f i r s t r e p o r t o f a n i n d i g e s t i b l e p l a n t p ig m e n t o r g ro u p o f p ig m e n t s

w as made b y R e id e t a l . ( 1 5 5 , 15 6 ) u s i n g 85 p e r c e n t a c e t o n e a s t h e s o l v e n t

f o r e x t r a c t i n g t h e p ig m e n t o r p ig m e n t s f ro m t h e f e e d and, f e c c s . T h i s

m e th o d w i l l be r e f e r r e d t o a s t h e p l a n t p ig m e n t r a t i o t e c h n i q u o . E s t i m a ­

19

t i o n s o f t h e c o n c e n t r a t i o n o f p l a n t p ig m e n t p r e s e n t i n t h e 85 p e r c e n t

a c e t o n e e x t r a c t s o f t h e f e e d and f e c e s -were mad© f ro m t h e am ount o f l i g h t

a b s o r b e d b y t h e d i l u t e d e x t r a c t s a t 40 6 m i l l i m i c r o n s wave l e n g t h u s i n g a

Be ckmann spe c t ro pho to m e te r .

The r e c o v e r y o f t h e e x t r a c t e d p l a n t p ig m e n t s i n t h e f e c e s w ere v e r y

c l o s e t o 100 p e r c e n t i n a l l o f t h e m a t e r i a l s s t u d i e d and t h e c a l c u l a t e d

d i g e s t i o n c o e f f i c i e n t s f ro m t h e p l a n t p ig m e n t r a t i o s showed e x c e l l e n t

a g r e e m e n t w i t h t h e c o n v e n t i o n a l t o t a l f e c a l c o l l e c t i o n t e c h n i q u e . Com­

p a r i s o n s w e re made b e tw e e n f i e l d - c u r e d h a y , b a r n - c u r e d h a y , o v e n - d r i e d

h a y , h a y - c r o p s i l a g e , l a d i n o c l o v e r h a y , an d t h r e e s t a g e s o f p a s t u r e

g r a s s .

W h i le R e id e t a l , ( 1 5 6 ) d i d n o t r e p o r t on t h e i d e n t i t y o f t h e p ig m e n t

o r p ig m e n t s t h a t w ere r e s p o n s i b l e f o r t h e l i g h t a b s o r p t i o n a t 406 m i l l i ­

m i c r o n s , t h e y f e l t t h a t one s u b s t a n c e was l a r g e l y r e s p o n s i b l e f o r t h e

a b s o r p t i o n o b s e r v e d .

M cC u llo u g h , E l l i o t a n d B a s t i n (1 2 2 ) h a v e made a p p l i c a t i o n o f t h e

p l a n t p ig m e n t r a t i o t e c h n i q u e d e s c r i b e d by R e id crfc a l . (1 5 6 ) f o r s t u d y i n g

t h e s e a s o n a l c h a n g e s i n t h e d i g e s t i b i l i t y o f t h e d r y m a t t e r an d p r o t e i n

o f p a s t u r e h e r b a g e t r e a t e d w i t h v a r i o u s ©mount o f b a r n y a r d m a n u re , b u t

d i d n o t make a c o m p a r i s o n w i t h an y o t h e r m ethod o f d e t e r m i n i n g d i g e s t i b i l ­

i t y c o e f f i c i e n t s .

The c o m m it te e o f j j j i ie r ica n S o c i e t i e s o f Agronomy, D a i r y S c i e n c e ,

A n im a l p r o d u c t i o n and Range M anagem ent (3 9 ) r e p o r t e d on p a s t u r e and r a n g e

r e s e a r c h t e c h n i q u e and p r o p o s e d t h a t t h e p l a n t p ig m e n t r a t i o m e thod s h o u ld

r e p l a c e t h e l i g n i n r a t i o t e c h n i q u e . Cook and H a r r i s (4 0 ) made a d i r e c t

c o m p a r i s o n o f t h e l i g n i n r a t i o m e th o d and t h e p l a n t p ig m e n t r a t i o m e thod

u s i n g s e v e n w e t h e r s h e e p g r a z e d on f i v e f o r a g e s p e c i e s i n n o r t h w e s t e r n

20

U ta h t h a t w e re t y p i c a l o f t h e n o r t h e r n d e s e r t s h r u b v e g e t a t i o n . A l l

s p e c i e s "were i n a d o rm a n t s t a g e and d i d n o t r e p r e s e n t t y p i c a l l u s h grow -

i n g v e g e t a t i o n . F e c e s w e re c o l l e c t e d f ro m f e c a l b a g s t h a t w e re e m p t ie d

t w i c e d a i l y and t h e s a m p le s c o m p o s i t e d o v e r a s i x - d a y g r a z i n g p e r i o d f o l l o w ­

i n g an e i g h t - d a y p r e l i m i n a r y p e r i o d . F o ra g e s a m p le s w ere t a k e n by m a n u a l ly

p l u c k i n g t h e p o r t i o n s o f t h e p l a n t t h a t w ere o b s e r v e d t o be g r a z e d by t h e

a n i m a l s . The ©mount o f p l a n t p ig jn e n t r e c o v e r e d i n t h e f e c e s o f s h e e p

g r a z i n g b i g s a g e b r u s h and b l a c k s a g e was c o n s i d e r a b l y l e s s t h a n t h a t c o n ­

sum ed. T h i s gave n e g a t i v e d i g e s t i o n c o e f f i c i e n t s a n d e x t r e m e l y low q u a n t i ­

t i e s o f e s t i m a t e d d r y m a t t e r i n t a k e . The p l a n t p ig m e n t r e c o v e r y i n t h e

f e c e s o f s h e e p g r a z i n g s q u i r r e l t a i l g r a s s seemed v e r y h i g h and gave a

c a l c u l a t e d c o e f f i c i e n t o f d i g e s t i b i l i t y f o r d r y m a t t e r o f 6 8 .7 p e r c e n t

w h ic h was m a r k e d ly h i g h e r t h a n a n y o t h e r o f t h e m a tu r e d o rm a n t d e s e r t

s p e c i e s s t u d i e d and seems e r r o n e o u s l y h i g h s i n c e i t i s a p p r o x i m a t e l y

50 p e r c e n t h i g h e r t h a n t h e d i g e s t i b i l i t y c o e f f i c i e n t o b t a i n e d b y t h e l i g -

n i n r a t i o t e c h n i q u e . T h i s i s t h e f i r s t i n d i c a t i o n t h a t t h e p l a n t p ig m e n t

r a t i o t e c h n i q u e w i l l n o t w ork w i t h c e r t a i n s p e c i e s o f f o r a g e * I t i s s i g ­

n i f i c a n t t h a t t h e y s e c u r e d c l o s e c h o c k s b e tw e e n t h e l i g n i n r a t i o m e thod

and t h e p l a n t p ig m e n t r a t i o m ethod w hen u s i n g a l f a l f a h e y .

F e i d e t a l . ( 1 5 4 , 1 5 5 , 1 5 6 ) h av e r e c e n t l y shown t h a t t h e p l a n t p i g ­

m en t c o n t e n t o f t h e g r a s s consum ed end t h e f e c e s v o i d e d a r e r e l a t e d to

t h e d e g r e e o f d i g e s t i b i l i t y , t o t h e s t a g e o f g ro w th , and t o t h e l e a f t o

s te m r a t i o . The r e l a t i o n s h i p b e tw e e n th e p l a n t p ig m e n t c o n t e n t o f d r y

f e c e s and t h a t o f t h e consum ed f o r a g e on a d ry w e i g h t b a s i s was e s t a b ­

l i s h e d w i t h c o n v e n t i o n a l d i g e s t i o n t r i a l s and i s e x p r e s s e d by t h e e q u a t i o n :

Y = ( 0 .0 9 25 X + 1 5 7 .3 3 8 3 l o g X) - 2 4 2 .1 1 8 1 , w here

Y = p l a n t p ig m e n t c o n t e n t p e r u n i t o f d r y m a t t e r o f consum ed f o r a g e and

X = p l a n t p ig m e n t c o n t e n t p e r u n i t o f f e c a l d r y m a t t e r .

C o n s i d e r i n g t h e d i f f i c u l t i e s e n c o u n t e r e d i n m a n u a l ly s a m p l in g p a s t u r e

f o r a g e t h a t i s c o m p a r a b le t o t h a t a c t u a l l y g r a z e d b y t h e a n i m a l , t h i s

m e th o d s h o u ld o f f e r a n e x c e l l e n t m eans o f o b t a i n i n g a r e p r e s e n t a t i v e con ­

c e n t r a t i o n o f p l a n t p ig m e n t i n t h e f o r a g e consum ed s im p ly by a n a l y z i n g

t h e f e c e s and a p p l y i n g t h e e q u a t i o n . R e id o t a l . ( 1 5 7 , 158) h a v e a l s o

fo u n d t h a t a d i f f e r e n t r e l a t i o n s h i p h o l d s b e tw e e n t h e p l a n t p ig m e n t c o n ­

c e n t r a t i o n i n d r y h a y s and t h e i r c o r r e s p o n d i n g f e c e s t h a n t h a t r e p o r t e d

w i t h f r e s h g r e e n g r a s s e s .

The p l a n t p ig m e n t r a t i o t e c h n i q u e h a s b e e n u s e d b y h o l l e r , H i l l and

L u n d q u i s t (1 3 0 ) t o d e t e r m i n e t h e a p p a r e n t d i g e s t i b i l i t y o f f o r a g e g r a z e d

by m i l k i n g cow s , b u t t h e m e thod w as n o t co m p ared w i t h a n y o t h e r t e c h n i q u e .

O th e r D i g e s t i o n T r i a l T e c h n iq u e s

I n c r e a s e d i n t e r e s t i n t h e a p p l i c a t i o n o f t h e r a t i o t e c h n i q u e s u t i l ­

i z i n g e i t h e r n a t u r a l l y - o c c u r r i n g p l a n t s u b s t a n c e s o r added m a t e r i a l s a s

i n d i c a t o r s f o r t h e d e t e r m i n a t i o n o f d i g e s t i b i l i t y i n r u m i n a n t s w i l l u n ­

d o u b t e d l y r e v e a l a num ber o f u s e f u l s u b s t a n c e s i n b o t h o f t h e s e c l a s s e s .

C o rb in a n d F o r b e s (4-2) f e d e l e v e n lam bs g ro u n d a l f a l f a t w i c e d a i l y

and gave n i n e t e s t lam b s e a c h 0 . 5 gram o f a n t h r a q u i n o n e v i o l e t b e f o r e e a c h

f e e d i n g and t h e two c o n t r o l lam bs r e c e i v e d p l a c e b o s . The dye ’was e x t r a c t e d

f ro m t h e f e c e s w i t h b e n z e n e i n a 11/ a r i n g m i c r o - b l e n d e r and d e n s i t y d e t e r ­

m i n a t i o n s w e re made w i t h a Beckman s p e c t r o p h o t o m e t e r on t h e b e n z e n e

s o l u t i o n o f t h e dye a t 578 m i l l i m i c r o n s . R e c o v e r i e s o f a n th ra q u in o n e -

v i o l c t f ro m t h e f e c e s o f n i n e lam bs r a n g e d f ro m 9 6 , 4 t o 1 0 6 . 0 p e r c e n t

w i t h a n a v e r a g e o f 1 0 0 .5 p e r c e n t . T h i s a s s u r e d t h a t d i g e s t i b i l i t y c o ­

e f f i c i e n t ' s c a l c u l a t e d by t h e dye r a t i o and by t h e t o t a l f e c a l c o l l e c t i o n

22

t e c h n i q u e w o u ld be p r a c t i c a l l y i d e n t i c a l . I n a s t u d y o f t h e v a r i a t i o n i n

dye c o n c e n t r a t i o n o f f e c e s e x c r e t e d a t d i f f e r e n t t i m e s o f t h e d a y , i t w as

e v i d e n t t h a t t h e n o o n f e c e s h a d a h i g h e r dye c o n c e n t r a t i o n t h a n t h e m orn­

i n g o r n i g h t f e c e s w h ic h i n d i c a t e s t h a t a d e q u a te s a m p le s s h o u ld be c o l l e c t ­

ed a t d i f f e r e n t t i m e s d u r i n g t h e d a y w hen s© m oling b y a p a r t i a l c o l l e c t i o n

t e c h n i q u e .

S c h n e i d e r , L u c a s , P a v i e c h and c i p o l l o n i (1 6 6 ) p u b l i s h e d e q u a t i o n s f o r

p r e d i c t i n g t h e d i g e s t i o n c o e f f i c i e n t s o f n u t r i e n t s i n f e e d s f e d t o c a t t l e

and s h eep an d i n c o n c e n t r a t e s f e d t o s w in e . They t o o k i n t o a c c o u n t t h e

p e r c e n t a g e s o f s e v e r a l n u t r i e n t s anti, t h e ty p e o f f e e d i n v o l v e d . E q u a t i o n s

w e re p r e s e n t e d f o r e s t i m a t i n g t h e d i g e s t i b i l i t y c o e f f i c i e n t s f o r o r g a n i c

m a t t e r , c r u d e p r o t e i n , c ru d e f i b e r , n i t r o g e n - f r e e e x t r a c t , e t h e r e x t r a c t ,

an d t h e c o n t e n t o f t o t a l d i g e s t i b l e n u t r i e n t s i n f o o d s , u s i n g t h e i r p e r ­

c e n t a g e s o f c r u d e p r o t e i n , c r u d e f i b e r , n i t r o g e n - f r e e e x t r a c t , and e t h e r

e x t r a c t a s p r e d i c t i n g f a c t o r s . T h e i r c a l c u l a t i o n s i n d i c a t e d t h a t t h e u s e

o f e q u a t i o n s w i l l r e s u l t i n p r e d i c t i o n e r r o r v a r i a n c e s w h ic h a r e 25 t o 4-5

p e r c e n t b e lo w t h o s e s e c u r e d i f a v e r a g e d i g e s t i o n c o e f f i c i e n t s f ro m p r e ­

p a r e d t a b l e s a r e e m p lo y e d .

F r a n c o i s (7 4 ) a l s o p r e s e n t e d f o r m u l a s and t a b l e s f o r o b t a i n i n g t h e

c o e f f i c i e n t o f d i g e s t i b i l i t y o f o r g a n i c m a t t e r end p r o t e i n a s a f u n c t i o n

o f t h e ©mount o f c e l l u l o s e i n t h e d ry m a t t e r .

S c h n e i d e r e t a l . (1 6 4 ) s i m p l i f i e d tlx ; e q u a t i o n f o r m e r l y p r e s e n t e d

( 1 6 6 ) t o e s t i m a t e t h e d i g e s t i o n c o e f f i c i e n t s o f c r u d e p r o t e i n , c ru d e f i b e r ,

n i t r o g e n - f r e e e x t r a c t , and e t h e r e x t r o u t a n d th e c o n t e n t o f t o t a l d i g e s t ­

i b l e n u t r i e n t s i n f e e d s f o r w h ic h fe w o r no d i g e s t i b i l i t y d a t a a r c a v a i l ­

a b l e . The e q u a t i o n u s e s t h e p e r c e n t a g e c o m p o s i t i o n o f c r u d e p r o t e i n ,

c r u d e f i b e r , n i t r o g e n - f r e e e x t r a c t and e t h e r e x t r a c t as p r e d i c t i n g f a c t o r s

and t h e a p p r o p r i a t e c o n s t a n t f o r t h e d i g e s t i o n c o e f f i c i e n t b e i n g c a l c u l a t e d .

o*z

Th© a u t h o r s p o i n t o u t t h a t t h i s e q u a t i o n d o e s n o t g iv e a s p r e c i s e an

e s t i m a t e o f th© d i g e s t i o n c o e f f i c i e n t a s t h e e q u a t i o n p r e v i o u s l y r e p o r t e d

w h ic h was d e s i g n e d f o r u s e w i t h f e e d s on w h ich s u f f i c i e n t d i g e s t i b i l i t y

d a t a a r e a v a i l a b l e w i t h t h e a n i m a l s p e c i e s d e s i r e d *

FACTORS AFFECTING THE DIGESTIBILITY OF ROUGHAGES

E f f e c t o f C rude F i b e r on D i g e s t i b i l i t y

The d e f i n i t i o n o f c r u d e f i b e r s e t up by H e n n e b e rg and S tohm ann ( 9 1 ) ,

b a s e d on a m e thod d e v i s e d b y th e m an d known a s t h e Weende m eth o d f o r e s t i m ­

a t i n g c r u d e f i b e r , c o n s i s t s o f t h e r e s i d u e a f t e r t r e a t m e n t w i t h 1 ,2 5 p e r ­

c e n t s u l f u r i c a c i d , 1 ,2 5 p e r c e n t p o t a s s i u m h y d r o x i d e , w a t e r , a l c o h o l and

e t h e r an d i s e s s e n t i a l l y t h e m ethod m o s t w i d e l y u s e d t o d a y . T h is i n c l u d e s

a m i x t u r e o f c h e m ic a l s u b s t a n c e s f ro m t h e p l a n t c e l l membrane w h ic h i s

p r i m a r l y c e l l u l o s e , h e m i c e l l u l o s e and o t h e r e n c r u s t i n g s u b s t a n c e s , s u c h

a s l i g n i n , c u t i n , s u b e r i n and p e c t i n s .

I t was o r i g i n a l l y i n t e n d e d t h a t t h e c ru d e f i b e r f r a c t i o n s h o u ld

r e p r e s e n t t h e r e l a t i v e l y i n d i g e s t i b l e f r a c t i o n o f t h e c a r b o h y d r a t e s w h i le

t h e n i t r o g e n - f r e e e x t r a c t s h o u ld i n c l u d e t h e m ore r e a d i l y d i g e s t i b l e p o r ­

t i o n . I t i s now w ^ l l -k n o w n t h a t t h e c r u d e f i b e r f r a c t i o n I s d i g e s t e d t o

a c o n s i d e r a b l e e x t e n t a n d , i n some cases, t o a, g r e a t e r e x t e n t t h a n t h e

n i t r o g e n - f r e e e x t r a c t . The n i t r o g e n - f r e e e x t r a c t a l s o c o n t a i n s v a r y i n g

am o u n ts o f r e l a t i v e l y i n d i g e s t i b l e c o n s t i t u e n t s , i n c l u d i n g l i g n i n .

C ram p to n ( 4 3 ) r e p o r t e d t h a t i n r o u g h a g e s , p a r t i c u l a r l y p a s t u r e s , t h e

c r u d e f i b e r f r a c t i o n i s f r e q u e n t l y more d i g e s t i b l e t h a n t h e n i t r o g e n -

f r e e e x t r a c t . C ram pton and M aynard (4 6 ) r e p o r t e d t h e d i g e s t i b i l i t y co ­

e f f i c i e n t s o f c r u d e f i b e r and n i t r o g e n - f r e e e x t r a c t f o r t h r e e c l a s s e s o f

r o u g h a g e s a i d f o r c o n c e n t r a t e s en d t h e p e r c e n t o f c a s e s i n w h ich t h e

c r u d e f i b e r w as a s h i g h l y d i g e s t e d a s t h e n i t r o g e n - f r e e e x t r a c t . T hese

d a t a ar© sum m arized i n T ab le 2 .

Table 21A v erag e D i g e s t i o n C o e f f i c i e n t s o f F e e d s b y R u m in an ts

K in d o f F eed Ho. o f C a se s

G o o f f , o f D i g e s t i b i l i t y C rude F i b e r H .F .E .

% w i t h C rude F i b e r a s h i g h as 1T.F.E.

D ry R o u g h a g e s 110 5 2 .4 5 9 .5 39

P a s t u r e H e rb a g e 12 7 5 .5 7 1 .4 67

S i l a g e 25 5 8 .2 6 4 .6 28

C o n c e n t r a t e s 88 5 3 .3 7 8 .5 10

■j_From C ram p to n and M aynard ( 4 6 ) .

Armsby ( 5 ) s t a t e d t h a t c r u d e f i b e r c o n t a i n e d m o s t o f t h e c e l l u l o s e ,

l i g n i n , c u t i n , a n d some o f t h e more d i f f i c u l t l y s o l u b l e h e m i c e l l u l o s e s .

H eadden ( 8 9 ) f o u n d t h a t t h e c r u d e f i b e r o f a l f a l f a c u t i n e a r l y b loom

s t a g e c o n t a i n e d 7 9 .0 p e r c e n t c e l l u l o s e and 2 1 .0 p e r c e n t l i g n i n .

Rorman (1 5 3 ) c o n c l u d e d t h a t t h e c ru d e f i b e r d e t e r m i n a t i o n i s m i s ­

l e a d i n g b e c a u s e t h e f r a c t i o n o b t a i n e d d o c s n o t b e a r an y d e f i n i t e r e l a t i o n ­

s h i p t o t h e s t r u c t u r a l c o n s t i t u e n t s o f t h e m a t e r i a l f ro m w h ic h i t i s o b ­

t a i n e d . He r e p o r t e d t h e c e l l u l o s e and l i g n i n c o n t e n t s o f t h e c r u d e f i b e r

from, s e v e r a l f e e d s and fo u n d t h a t t n e more h i g h l y l i g n i f i e d m a t e r i a l s do

n o t n e c e s s a r i l y y i e l d a c r u d e f i b e r h ig h i n l i g n i n .

Louw (1 1 3 ) made a s tu d y o f t h e d i g e s t i b i l i t y o f t h e v a r i o u s c e 1 1 -

w a l l c o n s t i t u e n t s o f g r a s s e s a s a f f e c t e d by t h e s t a g e o f m a t u r i t y , u s i n g

m a t e r i a l f ro m e a r l i e r d i g e s t i b i l i t y t r i a l s . The g r a s s s a m p le s w ere a

m i x t u r e o f v e l d g r a s s e s grown i n S o u th A f r i c a and w ere c u t a f t e r p e r i o d s

o f i 2 , 3 a n d 4 m o n th s o f u n d i s t u r b e d g ro w th . I n t h e s e g r a s s m i x t u r e s

and i n t h e f e c c s f ro m s h e e p co n su m in g th e m a s t h e i r e n t i r e r a t i o n , e s t i m ­

a t i o n s w e re made o f c e l l u l o s e , l i g n i n , t o t a l f u r f u r a l y i e l u , x y l a n n o m

c e l l u l o s e , u r o n i c a c i d a n h y d r i d e s , p e n t o s a n s , h e m i c e l l u l o s c s , c o l d w a t e r

s o l u b l e f r a c t i o n , c r u d e p r o t e i n , e t h e r e x t r a c t a n d t o t a l a s h ; a s w e l l a s

t h e am ount an d c o m p o s i t i o n o f t h e c r u d e f i b e r I n t h e g r a s s and f e c c s .

W ith i n c r e a s i n g m a t u r i t y o f t h e g r a s s , t h e p e r c e n t a g e o f n a t u r a l c e l l u l o s e

and t h e r a t i o o f xy l& n to t r u e c e l l u l o s e i n c r e a s e d s l i g h t l y * The i n c r e a s e

i n t h e l i g n i n and h e m i c e l l u l o s e c o n t e n t s vmre r e l a t i v e l y s m a l l . The d i ­

g e s t i b i l i t y t r i a l s showed t h e t r u e c e l l u l o s e t o be t h e m o s t d i g e s t i b l e

©nd t h e l i g n i n t h e l e a s t d i g e s t i b l e o f t h e c e 11- w a l l c o n s t i t u e n t s , b u t

a l l t h e c o n s t i t u e n t s showed d e c r e a s i n g d i g e s t i b i l i t y w i t h a d v a n c in g ma­

t u r i t y . The d i g e s t i b i l i t y o f t h e h e m i c e l l u l o s e s l a y b e tw e e n t h e v a l u e s

f o r t r u e c e l l u l o s e and l i g n i n , b e i n g c o n s i d e r a b l y lo w e r t h a n t h a t o f t r u e

c e l l u l o s e . E x a -m in a t io n o f t h e c r u d e f i b e r i s o l a t e d f ro m t h e g r a s s o r f ro m

t h e f e c e s showed t h a t t h e m a t e r i a l from g r a s s c o n t a i n e d a n a v e r a g e o f 9 6 .5

p e r c e n t n a t u r a l c e l l u l o s e , t h e r e m a in d e r c o n s i s t i n g m o s t l y o f l i g n i n . The

m a t e r i a l i s o l a t e d f r o m f e c e s c o n t a i n e d 9 2 .8 p e r c e n t n a t u r a l c e l l u l o s e and

a b o u t 10 p e r c e n t l i g n i n . I t i s e v i d e n t f ro m t h e i r d a t a t h a t t h e v a r i o u s

c o n s t i t u e n t s o f t h e c e l 1- w a l l showed a v a r y i n g r e s i s t a n c e t o t h e r e a g e n t s

u s e d i n t h e Weende m e thod f o r e s t i m a t i n g c r u d e f i b e r and t h e r e f o r e t h e

am o u n ts o f t h e s e c o n s t i t u e n t s r e c o v e r e d i n t h e c r u d e f i b e r showed c o n ­

s i d e r a b l e v a r i a t i o n . From 86 t o 93 p e r c e n t o f t h e t r u e c e l l u l o s e , 33 to

40 p e r c e n t of t h e x y l a n i n c e l l u l o s e , 12 t o 15 p e r c e n t o f t h e l i g n i n and

o n l y a b o u t 1 t o 4 p e r c e n t o f t h e p e n t o s a n i n h e m i c e l l u l o s e w ere r e c o v e r e d .

C o m p a r is o n s by v a r i o u s i n v e s t i g a t o r s o n t h e e f f e c t o f t h e c o n t e n t o f

c r u d e f i b e r on t h e d i g e s t i b i l i t y o f r o u g h a g e s m u s t t a k e I n t o c o n s i d e r a t i o n

t h a t d i f f e r e n t a n a l y t i c a l m e th o d s f o r c r u d e f i b e r g iv e w i d e l y d i f f e r e n t

r e s u l t s . T h i s h a s b e e n p o i n t e d o u t by j j o r d f e l d t e t a l . (1 3 2 ) who showed

t h a t t h r e e d i f f e r e n t m e th o d s f o r t h e d e t e r m i n a t i o n o f c r u d e f i b e r gave

e f f e c t o f c r u d e f i b e r c o n t e n t on d i g e s t i b i l i t y may be e x p r e s s e d b y t h e

e q u a t i o n , Y = 9 0 .1 - 0 .8 9 7 X , whe r e

Y - d i g e s t i b i l i t y o f t h e d r y m a t t e r and

X * c r u d e f i b e r c o n t e n t o f t h e f e e d .

D u ck w o rth (5 7 ) fo u n d a c l o s e n e g a t i v e c o r r e l a t i o n b e tw ee n t h e c r u d e

f i b e r c o n t e n t and t h e d i g e s t i b i l i t y c o e f f i c i e n t s o f r o u g h a g e s . D i j k s t r a

( 5 3 ) h a s c a l c u l a t e d f o r m u l a s f o r e s t i m a t i n g t h e s t a r c h e q u i v a l e n t o f

a r t i f i c i a l l y d r i e d g r a s s f ro m t h e p e r c e n t a g e s o f c r u d e p r o t e i n an d c r u d e

f i b e r o r f r o m t h e c r u d e f i b e r a l o n s . Eomb (9 2 ) fo u n d a c l o s e c o r r e l a t i o n

b e tw e e n t h e c ru d e f i b e r c o n t e n t and d i g e s t i b i l i t y . Tifith h a y s and s i l a g e ,

t h e r e l a t i o n b e tw e e n l i g n i n c o n t e n t an d d i g e s t i b i l i t y seem ed m ore m a rk e d

t h a n b e tw e e n c r u d e f i b e r a n d d i g e s t i b i l i t y .

H a l l s w o r t h ( 8 5 ) u s e d th e p u b l i s h e d r e s u l t s o f d i g e s t i b i l i t y t r i a l s

b y o t h e r w o r k e r s t o show a l i n e a r r e l a t i o n b e tw e e n t h e p e r c e n t a g e o f c ru d e

f i b e r and t h e d i g e s t i b i l i t y o f t h e o r g a n i c m a t t e r o f f e e d i n g s t u f f s . A

l i n e a r r e l a t i o n was a l s o e s t a b l i s h e d b e tw ee n th e s t a r c h e q u i v a l e n t o f p a s ­

t u r e h e r b a g e and t h e c r u d e f i b e r c o n t e n t . The r e l a t i o n b e tw e e n s t a r c h c -

q u i v a l e n t an d c r u d e f i b e r f o r a w id e r a n g e o f p a s t u r e s p e c i e s a n d f i b e r

c o n t e n t s c o u l d be e x p r e s s e d b y t h e e q u a t i o n , S t a r c h E q u i v a l e n t - 7 3 .5 6 -

0 . 62X, w h e re

X t h e p e r c e n t a g e o f c r u d e f i b e r .

S i m i l a r r e s u l t s vie r e r e p o r t e d by J a r l ( 9 8 , 100) u s i n g th e r e s u l t s o f

p r e v i o u s l y c o n d u c te d d i g e s t i o n t r i a l s to com pare t h e f i b e r c o n t e n t o f

h a y s w i t h t h e d i g e s t i b i l i t i e s . He fo u n d a n e g a t i v e c o r r e l a t i o n b e tw e e n

t h e f i b e r c o n t e n t and t h e d i g e s t i b i l i t i e s o f th e h a y s . Axe I s so n ( 1 1 , 1 2 ,

1 3 , 1 4 ) a n d A x e l s s o n and E r i k s s o n (1 5 ) r e p o r t e d t h a t t h e c r u d e f i b e r c o n ­

t e n t o f r o u g h a g e s shows a h i g h n e g a t i v e c o r r e l a t i o n w i t h t h e d r y m a t t e r

28

d i g e s t i b i l i i y , A x e l s s o n ( 1 3 , 14 ) c o m p i le d t h e d a t a f ro m 757 d i g e s t i o n

t r i a l s made i n d i f f e r e n t p a r t s o f t h e Y/orld and com pared t h e d i g e s t i b i l i t y

c o e f f i c i e n t s o f c r u d e p r o t e i n , e t h e r e x t r a c t , n i t r o g e n - f r e e e x t r a c t , c r u d e

f i b e r and o r g a n i c m a t t e r t o t h e c r u d e f i b e r c o n t e n t o f t h e d r y m a t t e r o f

a l f a l f a , c l o v e r , c l o v e r - t i m o t h y m i x t u r e s and t i m o t h y f e d g r e e n , a s s i l a g e

o r a s hay* The c r u d e f i b e r c o n t e n t i n f l u e n c e d t h e d i g e s t i b i l i t y o f a l l t h e

n u t r i e n t s , t h a t o f t h e o r g a n i c m a t t e r d e c r e a s i n g by 0 .7 1 f o r e a c h i n c r e a s e

o f one p e r c e n t i n c r u d e f i b e r c o n t e n t .

N o r d f e l d t e t a l . (1 3 2 ) i n v e s t i g a t e d th e e f f e c t o f l i g n i n , c e l l u l o s e ,

p e n t o s a n s and c r u d e f i b e r on th e d i g e s t i b i l i t y o f t h e d r y m a t t e r o f t h e

r a t i o n and f o u n d t h a t c r u d e f i b e r was a s c l o s e l y c o r r e l a t e d w i t h d i g e s t i b i l ­

i t y o f t h e d r y m a t t e r a s a n y o f th e c o n s t i t u e n t s s t u d i e d . I f l i g n i n , c e l l ­

u l o s e an d p e n t o s a n s w ere d e t e r m i n e d s e p a r a t e l y and t h e i r t o t a l i n f l u e n c e

u p o n t h e d i g e s t i b i l i t y c a l c u l a t e d by p a r t i a l r e g r e s s i o n , t h e d i g e s t i b i l i t y

o f t h e d r y m a t t e r was fo u n d to h a v e l e s s d e v i a t i o n a ro u n d t h e l i n e o f

r e g r e s s i o n t h a n when c a l c u l a t e d f ro m c ru d e f i b o r a l o n e .

T h e re i s c o n s i d e r a b l e e v i d e n c e t h a t t h e op tim um f i b e r c o n t e n t o f t h e

d i e t v a r i e s w i t h t h e s p e c i e s o f a n i m a l , t h e ty p e o f r a t i o n f e d and. o t h e r

e n v i r o n m e n t a l f a c t o r s . A x e I s s o n ( 8 , 9 , 10) h a s p r o p o s e d t h a t a c e r t a i n

op tim um l e v e l o f f i b e r i s n e e d e d i n a r a t i o n i f t h e e n e r g y i s t o be u t i l i z e d

m o s t e f f i c i e n t l y . He b e l i e v e s t h e optim um l e v e l o f c ru d e f i b e r t o be b e ­

tw e e n 18 t o 23 p e r c e n t and p o i n t s o u t t h a t i n d i g e s t i b i l i t y t r i a l s w h e re

v a l u e s a r e o b t a i n e d by d i f f e r e n c e , i t i s d e s i r a b l e t h a t b o t h t h e b a s a l and

t h e s u p p le m e n ta r y r a t i o n s c o n t a i n t h e optim um am oun ts o f p r o t e i n and f i b e r .

A x e l s s o n ( 1 3 ) h a s a l s o com pared t h e r e l a t i v e a b i l i t i e s o f t h e p i g , h o r s e ,

c a t t l e an d s h e e p to d i g e s t t h e o r g a n i c m a t t e r o f t h e r a t i o n an d showed t h a t

w i t h sh e e p a n d c a t t l e t h e d i g e s t i b i l i t y f e l l a s t h e c r u d e f i b e r i n c r e a s e d

29

i n ' th e d i e t . Th© r e l a t i o n "between t h e d i g e s t a b i l i t y o f t h e o r g a n i c m a t t e r

and t h e c o n t e n t o f c r u d e f i b e r i n t h e r a t i o n o f c a t t l e and s h eep i s shown

by t h e e q u a t i o n , Y ~ 87*8 - 0 .8 3 X , w h e re Y i s t h e d i g e s t i b i l i t y o f t h e

o r g a n i c m a t t e r a n d X i s t h e p e r c e n t a g e o f c r u d e f i b e r i n t h e d i e t .

N o r d f e l d t je t a l . (1 3 1 ) c o n d u c te d a f e e d i n g e x p e r im e n t w i t h d i f f e r e n t

l e v e l s o f c r u d e f i b e r i n t h e r a t i o n o f d a i r y cow s. O th e r co m p o n en ts o f t h e

r a t i o n ( d i g e s t i b l e p r o t e i n and t o t a l d i g e s t i b l e n u t r i e n t s ) w ere k e p t c o n ­

s t a n t . F o u r d i f f e r e n t r a t i o n s w e re f e d , a s f o l l o w s ; A w i t h 60 p o u n d s o f

N a p i e r g r a s s , B w i t h 40 p o u n d s o f N a p ie r g r a s s , C w i t h 20 p o u n d s o f N a p i e r

g r a s s d a i l y p e r cow an d D w i t h no N a p ie r g r a s s . The n e c e s s a r y a m o u n ts o f

p r o t e i n and t o t a l d i g e s t i b l e n u t r i e n t s w ere made up w i t h p i n e a p p l e b r a n ,

s o y b e a n o i l m e a l , m e a t m e a l , f i s h m ea l and m o l a s s e s . The c r u d e f i b e r con ­

t e n t o f t h e s e f o u r r a t i o n s i n p e r c e n t a g e o f d r y m a t t e r was a s f o l l o w s ;

A, 2 2 . 7* B, 1 9 . 6 j C, 1 6 . l j a n d D, 1 2 .0 p e r c e n t . The e f f e c t o f t h e l e v e l

o f c r u d e f i b e r i n t h e f e e d u p o n m i l k p r o d u c t i o n was h i g h l y s i g n i f i c a n t .

l/7hen t h e c r u d e f i b e r c o n t e n t o f t h e f e e d w as i n c r e a s e d above 16 p e r c e n t ,

a d r o p i n m i l k p r o d u c t i o n o c c u r r e d . The a v e r a g e d a i l y 4 p e r c e n t f a t

c o r r e c t e d m i l k p r o d u c t i o n p e r cow f o r 12 w eeks w as 2 0 .6 p o u n d s on r a t i o n

A, 2 1 .7 p o u n d s on r a t i o n B, 2 3 .4 p o u n d s o n r a t i o n C, an d 2 3 .8 p o u n d s on

r a t i o n D* M i e t h e r o t h e r c o m b in a t i o n s o f f e e d s m ig h t h a v e a d i f f e r e n t

op tim um l e v e l o f c r u d e f i b e r i n t h e r a t i o n h a s n o t b e e n shown.

L a n c a s t e r ( 1 1 ) gave a n a l y t i c a l and d i g e s t i b i l i t y d a t a f o r 11 s u c c u ­

l e n t f e e d s and s i x r o u g h a g e s . L i g n i n , c e l l u l o s e and c r u d e f i b e r a l l h ad

a d e p r e s s i n g e f f e c t u p o n th e d i g e s t i b i l i t y o f o r g a n i c m a t t e r a s shown by

th e c o r r e l a t i o n c o e f f i c i e n t s o f - 0 , 9 7 8 , - 0 . 8 0 8 and - 0 . 9 4 4 f o r t h e d i g e s t ­

i b i l i t i e s o f t h e o r g a n i c m a t t e r and t h e p e r c e n t a g e c o n t e n t o f l i g n i n ,

c e l l u l o s e and c r u d e f i b e r , r e s p e c t i v e l y .

SO

McMeekan ( 1 2 3 ) a l s o c a l c u l a t e d a c o r r e l a t i o n c o e f f i c i e n t o f -0 * 9 4 4

b e tw e e n t h e c r u d e f i b e r c o n t e n t and t h e d i g e s t i b i l i t y o f t h e o r g a n i c

m a t t e r o f f e e d s r e p o r t e d b y Woodman (1 8 7 ) w h ic h i s i d e n t i c a l w i t h t h e

c o r r e l a t i o n c o e f f i c i e n t r e p o r t e d by L a n c a s t e r ( 1 1 0 ) ,

P h i l l i p s a n d L o u g h lin . ( 1 5 1 ) a n a l y z e d 25 s a m p le s o f e s s e n t i a l l y p u r e

s t a n d s o f f o r a g e f r o m v a r i o u s l a b o r a t o r i e s i n t h e U n i t e d S t a t e s t h a t h ad

s e r v e d a s t h e s o l e r a t i o n i n f e e d i n g e x p e r i m e n t s w i t h c a t t l e . The l i g n i n ,

p r o t e i n , c e l l u l o s e and c r u d e f i b e r c o n t e n t s o f t h e s a m p le s w ere a l l m ore

o r l e s s c l o s e l y r e l a t e d t o t h e i r y i e l d o f e n e r g y , b u t a t d i f f e r e n t l e v e l s

o f t h e s e c o n s t i t u e n t s f o r t i m o t h y and a l f a l f a , Y / i th in a s p e c i e s , c r u d e

f i b e r w as l e s s c l o s e l y c o r r e l a t e d w i t h d i g e s t i b i l i t y o f e n e r g y and d r y

msLtter t h a n was t h e l i g n i n c o n t e n t ,

S t e e n s b e r g and W i n th e r ( 1 7 5 ) c o n d u c t e d d i g e s t i b i l i t y t r i a l s w i t h

l u c e r n t a k e n a t e a r l y , n o rm a l an d l a t e f i r s t c u t t i n g s . The l a t e r c u t t i n g s

i n c r e a s e d i n c r u d e f i b e r c o n t e n t and t h e d i g e s t i b i l i t y o f t h e o r g a n i c

m a t t e r d e c r e a s e d ,

S o t o l a (1 7 1 ) d i d n o t g e t a c o n s i s t e n t r e l a t i o n b e tw e e n t h e c r u d e

f i b e r c o n t e n t o f w h e a t , o a t s and b a r l e y h a y s an d d i g e s t i b i l i t y o f t h e

v a r i o u s n u t r i e n t s w i t h i n c r e a s i n g m a t u r i t y . T h i s s t u d y i n c l u d e d r i p e

g r a i n s w h ic h p r o d u c e d a n i n c r e a s e d c ru d e f i b e r c o n t e n t o f t h e s te m s c o n ­

c o m i t a n t w i t h i n c r e a s e s i n t h e r e a d i l y d i g e s t e d c a r b o h y d r a t e s o f t h e

m a t u r i n g h e a d s . The r e l a t i o n s h i p b e tw e e n th e d i g e s t i b i l i t y o f t h e d r y

m a t t e r and t h e c r u d e f i b e r c o n t e n t o f th© s te m s an d l e a v e s o n l y w ou ld

l i k e l y g i v e c o n s i s t e n t r e s u l t s . T h i s a s s u m p t i o n i s p a r t i a l l y s u b s t a n ­

t i a t e d b y l a t e r w o rk b y S o t o l a (1 7 3 ) w i t h d i g e s t i b i l i t y s t u d i e s o f t h r e e

s t a g e s o f sm ooth b r o m e g r a s s . C rude f i b e r i n c r e a s e d f ro m 1 9 ,7 7 t o 3 5 .9 2

p e r c e n t w h i l e t h e p l a n t g re w f ro m 4 , 5 t o 36 i n c h e s i n h e i g h t . The d ry

31

m a t t e r w as 81 p e r c e n t d i g e s t i b l e a t t h e 4 * 5 - i n c h s t a g e and o n l y 5 5 ,8 p e r c e n t

d i g e s t i b l e a t t h e 3 6 - i n c h s t a g e *

S w i f t ejb a l * (1 7 8 ) c o n d u c t e d d i g e s t i b i l i t y t r i a l s w i t h la m b s and s h e e p

f e d a b a s a l d i e t o f good q u a l i t y o f a l f a l f a an d t i m o t h y h a y , c o r n m e a l an d

l i n s e e d c a k e m e a l , when c r u d e f i b e r s u p p le m e n t s i n th© fo rm o f s t r a w w ere

a d d e d , t h e d i g e s t i b i l i t y c o e f f i c i e n t s o f t h e p r o t e i n , e t h e r e x t r a c t , c r u d e

f i b e r and e n e r g y o f t h e w h o le r a t i o n d e c r e a s e d and t h e t o t a l am ount o f p r o ­

t e i n and e t h e r e x t r a c t d i g e s t e d was r e d u c e d .

F o r b e s and G a r r i g p s ( 7 0 ) fo u n d c o r r e l a t i o n c o e f f i c i e n t s o f - 0 . 7 4 f o r

s t e e r s and - 0 . 6 4 f o r w e t h e r s b e tw e e n t h e d i g e s t i b i l i t y o f t h e o r g a n i c m a t t e r

and t h e c r u d e f i b e r c o n t e n t o f g r a z e d f o r a g e s . The b e s t c o r r e l a t i o n b e tw e e n

c h e m ic a l c o m p o s i t i o n and o r g a n i c m a t t e r d i g e s t i b i l i t y was o b t a i n e d w i t h

l i g n i n *

R e id (1 5 3 ) r e c e n t l y r e p o r t e d a c o r r e l a t i o n c o e f f i c i e n t o f + 0 .8 8 5 b e tw e e n

th© c r u d e f i b e r c o n t e n t a n d t h e t o t a l d i g e s t i b l e n u t r i e n t s c o n t e n t o f t h e

g r a s s .

Crum pton and J a c k s o n (4 4 ) d i d n o t f i n d t h e c ru d e f i b e r c o n t e n t o f

p a s t u r e h e r b a g e t o be c l o s e l y c o r r e l a t e d t o s e a s o n a l c h a n g e s i n t h e d i ­

g e s t i b i l i t y o f t h e s e f o r a g e s *

A c o m p i l a t i o n o f t h e r e g r e s s i o n e q u a t i o n s r e l a t i n g t h e c ru d e f i b e r co n ­

t e n t o f a f e e d t o t h e d i g e s t i b i l i t y o f t h e d r y m a t t e r i s g i v e n i n T a b le 3 .

7 n

T a b le 3 .

R e g r e s s i o n e q u a t i o n s r e l a t i n g d i g e s t i b i l i t y o f d r y

m a t t e r t o c ru d e f i b e r c o n t e n t o f r a t i o n

R e g r e s s i o n E q u a t i o n C o r r e 1.C o e f f .

M a t e r i a l R e f e r e n c e

Y = 8 3 .0 - 0 .7 0 X

ii o » 03

'A l f a l f a P h i l l i p s I L o u g h l i n (1 5 1 )

Y = 1 3 0 .3 - 2,.14-X - 0 . 8 4 2 T im othy i) ii tt

v ^ 8 7 .8 - 0 .8 3 X ----- A x e l s s o n ( 1 5 ) .

Y = 8 6 .4 - 0 .8 4 X - 0 . 9 7 H o r d f e l d t ( 1 3 2 ) .

Y = 9 0 .1 - 0 .8 9 7 X - - — - O lo f s s o n ( 1 4 0 ) .

Y * 96 - 1 .0 0 X - 0 . 7 4 p a s t u r e ( S t e e r s )

F o rb e s andG a r r ig u s ( 7 0 ) .

Y = 94 - 1 .0 1 X - 0 . 6 4 P a s t u r e ( b o t h e r s )

F o r b e s andG a r r i g u s ( 7 0 ) .

E f f e c t o f C e l l u l o se C o n te n t on D i g e s t i b i l i t y

C e l l u l o s e c o m p r i s e s s u c h a l a r g o am ount o f t h e t o t a l d r y n a t t e r o f

m o s t f o r a g e s t h a t i t s a v a i l a b i l i t y t o t h o a n i m a l and i t s e f f e c t on t h e d i ­

g e s t i b i l i t y o f t h e o t h e r f e e d c o n s t i t u e n t s i s o f m a jo r i m p o r t a n c e a e s ­

p e c i a l l y i n r u m in a n t n u t r i t i o n * A lth o u g h t h e r e i s p . p a u c i t y o f i n f o r m a t i o n

on t h e r e l a t i o n o f c e l l u l o s e i n f o r a g e s t o t h e i r n u t r i t i v e v a l u e , t h e r e a r e

s e v e r a l r e p o r t s vrh icb i n d i c a t e t h a t th e e s t i m a t i o n o f c e l l u l o s e , l i g n i n ,

h e i f i i c c l l u l o s e s and o t h e r c a r b o h y d r a t e s -rov.ld Oiv o a b e t t e r i n d i c a t i o n o f

f o r a g e v a l u e t h a n a d o t e r m i n a t i o n o f th o c r u d e f i b e r c o n t o r t end c a l c u l a ­

t i o n o f t h e am ount o f n i t r o g e n - f r e e e x t r a c t . ( e f , C2, 1 0 1 , 1 1 7 , 1 3 3 , I d ,

1 6 1 ) .

33

T rue c e l l u l o s e i n a c h e m ic a l s e n s e i s & g l u c o s e p o l y s a c c h a r i d e y i e l d ­

i n g o n l y g l u c o s e o n h y d r o l y s i s . C e l l u l o s e i s fo rm ed i n m o s t p l a n t s i n

v e r y c l o s e a s s o c i a t i o n w i t h o t h e r p o l y s a c c a r i d e s and h a s h e x o s a n s and

p e n t o s a n s i n t e r m i x e d i n t h e c e l l u l o s e f i b e r s w h ic h fo rm a n o rm a l p a r t o f

t h e c e l l u l o s i c s t r u c t u r e * T hese s u b s t a n c e s t h a t a r e c l o s e l y a s s o c i a t e d

w i t h t h e t r u e c e l l u l o s e , and u n d e r some c o n d i t i o n s a r e e x t r a c t e d and r e ­

t a i n e d \ u i t h t h e t r u e c e l l u l o s e , h a v e b e e n c a l l e d t h e c e l l u l o s a n s b y H aw ley

and Norman ( 8 8 )* Norman (1 3 5 ) b e l i e v e s t h a t t h e c e l l u l o s a n s a r e l a i d down

w i t h t h e c e l l u l o s e a s i t i s fo rm ed and t h e two fo rm t h e m i c e l l a e o f t h e

f i b e r s * The m o l e c u l a r s i z e o f t h e c e l l u l o s a n s i s c o n s i d e r a b l y l e s s t h a n

t h a t o f t r u e c e l l u l o s e . The s u g a r u n i t s a r e j o i n e d by s e c o n d a r y v a l e n c i e s

w e a k e r t h a n t h o s e j o i n i n g t h e t r u e c e l l u l o s e u n i t s and s i n c e t h e c h a i n

l e n g t h i s s h o r t e r , t h e y may be l a r g e l y e x t r a c t e d u n d e r c o n d i t i o n s w h ic h

do n o t e x t r a c t t h e t r u e c e l l u l o s e * Norman and F u l l e r ( 1 3 8 ) b e l i e v e i t

u n l i k e l y t h a t c e l l u l o s e end t h e a s s o c i a t e d p o l y u r o n i d e h e m i c e l l u l o s e s and

l i g n i n a r e c h e m i c a l l y l i n k e d o r t h a t s o - c a l l e d "com pound” c e l l u l o s e s o c c u r ,

b u t t h a t t h e n o r m a l s t r u c t u r e i s s u c h t h a t i n t e r p e n e t r a t i n g s y s te m s a r e

f o u n d .

The n u t r i t i v e v a l u e o f c e l l u l o s e i s i n d i c a t e d b y Woodman and S t e w a r t

(1 9 0 ) who r e p o r t e d t h a t o v e r 90 p e r c e n t o f t h e d i g e s t i b l e c e l l u l o s e becom es

a v a i l a b l e i n t h e fo rm o f g lu c o s e and o n l y a b o u t 8 p e r c e n t im d e rg o e s f e r m e n ­

t a t i o n t o g a s o s and o r g a n i c a c i d s * C e l l u l o s e i s a t t a c k e d by v a r i o u s

b a c t e r i a t h a t fo rm e x t r a c e l l u l a r enzym es t h a t a t t a c k t h e c e l l u l o s e m o le ­

c u le * B o th a e r o b e s and a n a e r o b e s a r e known to be c a p a b le o f d e c o m p o s in g

o r a r e e v e n d e p e n d e n t o n c e l l u l o s e ( 9 4 , 1 2 1 , 1 3 8 ) . Woodman an d S t e w a r t

(1 9 1 ) s t u d i e d t h e b a c t e r i a l d e c o m p o s i t i o n o f t h e c ru d e f i b e r i s o l a t e d

f ro m v a r i o u s f e e d s a n d fo u n d t h e f e r m e n t a t i o n c o e f f i c i e n t s i n a l l c a s e s

34

h i g h e r t h a n t h e d i g e s t i o n c o e f f i c i e n t s d e t e r m in e d i n anim&l t r i a l s . A l s o ,

t n e c r u d e f i b e r f e r m e n t a t i o n c o e f f i c i e n t s f o r t h e u n t r e a t e d f e e d s w e re much

lo w e r t h a n t h e c o r r e s p o n d i n g v a l u e o b t a i n e d f r o m t h e s e p a r a t e d f i b e r . I h i s

w o u ld i n d i c a t e t h a t a s s o c i a t i o n o f t h e c e l l u l o s e w i t h o t h e r e n c r u s t i n g e e l l -

w a l l c o n s t i t u e n t s i n p l a n t m a t e r i a l s w ould be a l i m i t i n g f a c t o r i n t h e

c e l l u l o s e u t i l i z a t i o n by t h e a n i m a l . Woodman ( 1 8 7 ) a l s o r e p o r t e d 011 t h e

d i f f e r e n c e i n t h e d i g e s t i b i l i t y o f l i g n i f i e d and n o n - l i g n i f i e d f e e d i n g

s t u f f s . N o n l i g n i f i e d f e e d s s u c h a s s u g a r b e e t p u l p , m a n g o ld s , c a b b a g e an d

s u g a r b e e t t o p s showed c o e f f i c i e n t s o f d i g e s t i b i l i t y o f t h e c e l l u l o s e a s

8 9 . 7 , 7 8 . 0 , 7 4 . 0 and 7 1 . 6 p e r c e n t , r e s p e c t i v e l y . The c o e f f i c i e n t s o f d i ­

g e s t i b i l i t y o f t h e c e l l u l o s e o f s u c h l i g n i f i e d f e e d s a s o a t s t r a w , w h e a t

s t r a w , c o t t o n s e e d m e a l , l i n s e e d m e a l and w h e a t b r a n w ere o n l y 5 4 . 0 , 5 0 . 0 ,

3 7 .0 and 2 6 .0 p e r c e n t , r e s p e c t i v e l y .

Haumann (1 2 8 ) made a s tu d y o f t h e c ru d e f i b e r f r a c t i o n s f ro m r a t i o n s

u s e d i n s e v e r a l d i g e s t i b i l i t y t r i a l s w i t h sh e e p and o f t h e c o r r e s p o n d i n g

f e c e s . The d i g e s t i b i l i t y o f t h e c r u d e f i b e r a n d i t s p e n t o s a n and c e l l u l o s e

c o m p o n en ts showed w id e v a r i a t i o n w i t h d i f f e r e n t f e e d s and w as i n v e r s e l y

p r o p o r t i o n a l t o t h e l i g n i n c o n t e n t , w h ich was i n d i g e s t i b l e i n n e a r l y a l l

c a s e s . C ram p to n and M aynard (4 6 ) r e p o r t e d f e e d c e l l u l o s e t o be 6 2 .5 p e r ­

c e n t d i g e s t e d b y a s t e e r on e q u a l p a r t s o f a l f a l f a and g r a i n . O th e r c a r ­

b o h y d r a t e s c a l c u l a t e d by d i f f e r e n c e w ere 9 4 .8 p e r c e n t d i g e s t e d . R e id (1 5 3 )

r e p o r t e d t h e d i g e s t i o n c o e f f i c i e n t s o f c e l l u l o s e f r o m e a r l y , medium and

l a t e - c u t g r a s s a s 7 7 . 8 , 6 8 .5 and 6 1 . 0 , r e s p e c t i v e l y . S i m i l a r d e c r e a s e s

o c c u r r e d i n t h e d i g e s t i b i l i t y o f t h e d r y m a t t e r .

The c e l l u l o s e c o n t e n t o f g r a s s e s , e x p r e s s e d a s a p e r c e n t a g e o f t h e

d r y m a t t e r o r o f t h e c a r b o h y d r a t e f r a c t i o n , i s much h i g h e r t h a n t h a t o f

le g u m e s ; t h u s g i v i n g h i g h e r c r u d e f i b e r c o n t e n t s i n g r a s s e s t h a n i n le g u m es

( 6 ).

35

Much o f th© r e p o r t e d work o n t h e d i g e s t i b i l i t y o f c e l l u l o s e may h a v e

b e e n i n f l u e n c e d b y o t h e r f a c t o r s i n t h e r a t i o n a f f e c t i n g d i g e s t i b i l i t y ,

R e c e n t w ork h a s shown, t h a t t h e d i g e s t i o n o f ro u g h a g e by c a t t l e w as i n ­

c r e a s e d b y a d d i t i o n o f p r o t e i n , ( 3 1 , 34 , 36 ) an d a l s o by a w a t e r e x t r a c t

o f a l f a l f a h a y an d t h e a s h f ro m good q u a l i t y a l f a l f a h a y ( 33 ) .

B u r ro u g h s e t a l . ( 3 0 ) h a v e r e c e n t l y r e p o r t e d a n a r t i f i c i a l rum en

t e c h n i q u e f o r s t u d y i n g c e l l u l o s e d i g e s t i o n i n r o u g h a g e s . U s in g t h i s t e c h ­

n i q u e , B u r ro u g h s e t a l . (3 5 ) s t u d i e d t h e e f f e c t o f s u p p le m e n t s o f a v a i l ­

a b l e n i t r o g e n , a c o m p lex m i n e r a l m i x t u r e and a n a u t o c l a v e d e x t r a c t o f

cow m an u re o n t h e d i g e s t i o n o f f o u r p o o r q u a l i t y r o u g h a g e s ( c o r n , s t o v e r ,

w h e a t s t r a w , c o r n c o b s , and m a tu re t i m o t h y - b l u e g r a s s h a y ) and f o u r good

q u a l i t y d e h y d r a t e d f o r a g e s ( c l o v e r h a y , r y e h a y an d two l o t s o f a l f a l f a

h a y ) . The c e l l u l o s e i n t h o good q u a l i t y ro u g h a g e s was d i g e s t e d e f f i ­

c i e n t l y w i t h o u t s u p p l e m e n t a t i o n , w i t h no i n c r e a s e d d i g e s t i o n o c c u r r i n g

whfemi t h e co m p le x m i n e r a l s a n d a u t o c l a v e d m anure e x t r a c t w e re i n c l u d e d .

The c e l l u l o s e i n t h e p o o r q u a l i t y ro u g h a g e s w as n o t d i g e s t e d e f f i c i e n t l y

w i t h o u t s u p p l e m e n t a t i o n . The a d d i t i o n o f c o m p lex m i n e r a l s , m anure e x t r a c t

o r a v a i l a b l e n i t r o g e n g r e a t l y i n c r e a s e d t h e d i g e s t i o n o f c e l l u l o s e i n t h e s e

p o o r q u a l i t y r o u g h a g e s .

B u r ro u g h s e t a l . ( 3 6 ) a l s o s t u d i e d t h e e f f e c t o f s e v e r a l c e r e a l

g r a i n s and p r o t e i n - r i c h f o o d s w i t h r e s p e c t t o t h e i r a b i l i t y t o i n c r e a s e

t h e d i g e s t i o n o f c e l l u l o s e by rumen m i c r o o r g a n i s m s . T h e i r r e s u l t s showed

t h a t d r i e d d i s t i l l e r s s o l u b l e s , s o y b e a n o i l m e a l and l i n s e e d o i l m e a l gave

t h e g r e a t e s t i n c r e a s e i n ro u g h a g e d i g e s t i o n . Cane m o l a s s e s , c o r n , w h e a t

b r a n and c o t t o n s e e d m e a l h ad l e s s e f f e c t and. m e a t s c r a p s , f i s h m e a l , l i v e r

m e a l and o a t s h ad l i t t l e o r no i n f l u e n c e on ro u g h a g e d i g e s t i o n by m i c r o ­

o r g a n i s m s i n t h o a r t i f i c i a l rum en .

E f f e c t o f L i g n i n C o n te n t on D i g e s t i b i l i t y

L i g n i n h a s b e e n q u i t e w i d e l y s t u d i e d i n f o r a g e p l a n t s and i s q u i t e

l o g i c a l l y a s s o c i a t e d w i t h t h e d i g e s t i b i l i t y o f t h e o t h e r f e e d c o n s t i t u e n t s

s i n c e i t i s g e n e r a l l y c o n s i d e r e d a s a b i o l o g i c a l l y i n e r t c o n s t i t u e n t w h ic h

i n c r e a s e s w i t h a d v a n c i n g m a t u r i t y o f t h e p l a n t , ( 6 , 4 6 , 1 3 4 , 1 4 8 , 1 5 9 ,

1 9 1 ) .

An i n c r e a s e i n t h e l i g n i n c o n t e n t o f p l a n t m a t e r i a l i s u s u a l l y a s s o ­

c i a t e d w i t h a d e c r e a s e i n i t s d i g e s t i b i l i t y ( 1 8 , 4 3 , 4 6 , 6 9 , 1 1 0 , 1 1 9 , 1 2 0 ,

1 4 1 , 1 7 6 , 1 8 7 ) .

L i g n i n h a s b e e n r e p o r t e d t o be i n d i g e s t i b l e by s t e e r s (4-6); by co'ws

on a l f a l f a h a y ( 8 4 ) ; by sh e e p ( 8 3 ) ; by cows on a m ix ed f e e d and b y sh e e p

o n d r i e d S udan g r a s s ( 6 2 ) ; try sh e e p on m ix e d f e e d s ( 1 7 8 ) ; by s h e e p on

c l o v e r - t i m o t h y h a y ( 6 8 ) ; by sh e e p on K o re a n l e s p e d e z a h a y c u t a t f o u r

s t a g e s o f m a t u r i t y ( 4 1 ) ; by. cow s on a r a t i o n o f a l f a l f a s i l a g e , c o r n

s i l a g e and g r a i n a n d a l s o on a r a t i o n o f a l f a l f a h a y , c o r n s i l a g e and

g r a i n ( 1 0 3 ) .

C so h k a , P h i l l i p s and J o n e s (4 8 ) f e l t t h a t l i g n i n 'was dome t h o x y l a t e d

o r t h a t d e g r a d a t i o n o f l i g n i n o c c u r r e d i n t h e r u m in a n t d i g e s t i v e t r a c t

s i n c e d e t e r m i n a t i o n s o f t h e m e th o x y l g ro u p on th e l i g n i n f e d and t h a t

e l i m i n a t e d i n t h e f e c e s i n d i c a t e d t h a t l i g n i n l o s t a p o r t i o n o f t h e

m e th o x y l g ro u p s i n p a s s i n g t h r o u g h t h e a n im a l b o d y . Tilhen l i g n i n w as

f e d t o cows an i n c r e a s e i n b e n z o i c a c id e l i m i n a t i o n i n t h e u r i n e was

o b s e r v e d w h ic h was b e l i e v e d t o be d e r i v e d f ro m l i g n i n d e g r a d a t i o n p r o ­

d u c t s . p a z u r a n d D^Long ( 1 4 5 ) d e t e r m in e d t h e h i p p u r i c and b e n z o i c a c i d

e x c r e t i o n o f s h e e p f e d c l o v e r h a y c u t a t f i v e s t a g e s o f m a t u r i t y and

f o u n d t h a t a b o u t t h r e e t i m e s a s much h i p p u r i c a c id w as e x c r e t e d by th o

s h e e p f e d th© e a r l y - c u t c l o v e r a s b y t h e s h e e p f e d t h e m a tu re c l o v e r .

37

Since they f e l t th a t th ese were excretory products o f l ig n in breakdown, i t

in d ica ted a greater degradation o f the lig j iin in the younger c lover than in

the more mature c lover fed to sheep*

MeJLnally (119) reported a lo s s o f l ig n in during d ig e stio n o f straw in

the rumen and a lso w ith rumen conten ts in v i t r o * Bondi and Meyer (27) re­

ported th a t the d ig e s t ib i l i t y c o e f f ic ie n t s o f l ig n in w ith sheep ranged be­

tween 35 and 64, depending upon the p lan t m ateria l fed* They a lso reported

th a t fe c e s l ig n in gave lower methoxyl va lu es than p lant l ig n in which they

b elieved in d icated an attack on th e l ig n in m olecule during passage through

the d ig e s t iv e tract* Louw (113) reported th a t sheep were able to d ig e s t

24.5 percent o f the l ig n in in grass one-month-old and on ly 11*6 percent

when the *>am& grass four months o ld . Davis e t a l . (50) found the d i­

g e s t i b i l i t y o f l i gnin in pea v in e s and lim a bean v ines as 16*0 and 10 .6

percen t, resp ectiv e ly *

E l l i s , Matrone and Maynard (62) and Gray (83) have used an enzymatic

d ig e stio n follow ed by a d ilu te acid treatm ent before allow ing the m ateria l

to react w ith the strong acid in the determ ination o f l ig n in . They have

shown w ith th is method o f determ ination th a t the l ig n in o f cer ta in forages

i s com pletely in d ig e stib le * Crampton and Maynard (46) had p rev iou sly re­

ported l ig n in to be d ig e s t ib le to the ex ten t o f more than 30 percent in

feed b ar ley , wheat screen ings and feed o a ts , but was alm ost com pletely

in d ig e s t ib le by the m od ifica tion o f Crampton and Ifh iting (47) in which

the l ig n in i s determined by d iffe r e n c e . The p r in c ip a l source o f d is ­

crepancy may be the varying proportions o f n on -lign in m ateria ls accounted

fo r by the d if fe r e n t methods o f determ ination. The n egative d ig e st io n

c o e f f ic ie n t s reported o cca s io n a lly are probably explained on the b a s is o f

sm aller n itrogen conten ts o f the l ig n in is o la te d from the feeds than are

obtained from the l ig n in iso la te d from the fe c e s . Armitage, Ashworth and

F e r g u s o n ( 4 ) h av e s u g g e s t e d a p r e l i m i n a r y t r e a t m e n t w i t h t r y p s i n an d d i l u t e

a c i d t o m in im iz e t h i s e r r o r .

L a n c a s t e r (1 1 0 ) r e p o r t e d t h e c o r r e l a t i o n c o e f f i c i e n t s o f t h e am oun t o f

l i g n i n w i t h t h e c o n t e n t and d i g e s t i b i l i t y o f o t h e r p l a n t c o n s t i t u e n t s . The

r e s u l t s a r e shown i n T a b l e 4 .

T a b le 4 .

C o r r e l a t i o n C o e f f i c i e n t s o f L i g n i n U i th O th e r F eed C o n s t i t u e n t s

p e r c e n t d i g e s t i o n o f o r g a n i c m a t t e r - 0 .S 7 8

Pe r c e n t d i g e s t i o n o f c r u d e f i b e r -0 * 9 5 4

p e r c e n t d i g e s t i o n o f c e l l u l o s e - 0 .9 1 S

P e r c e n t d i g e s t i o n o f p e n t o s a n s - 0 .9 0 6

Crude f i b e r c o n t e n t o f f e e d + 0 .9 5 5

C e l l u l o s e c o n t e n t o f feed. +C .770

^From L a n c a s t e r ( 1 1 0 ) .

Swanson and lie rm an (1 7 6 ) found t h e d i g e s t i b i l i t y o f p r a c t i c a l l y a l l

o f t h e d e t e r m i n e d n u t r i e n t s o f K orean l e s p e d e z a h a y d e c r e a s e d as t h e ma­

t u r i t y a d v a n c e d and t h e l i g n i n c o n t e n t i n c r e a s e d .

A c o m p i l a t i o n o f p u b l i s h e d r e g r e s s i o n e q u a t i o n s r e l a t i n g t h e l i g n i n

c o n t e n t an d th© d i g e s t i b i l i t y o f t h e d ry m a t t e r i s g iv e n i n T a b le 5.

39

T a b le 5 ,

R e g r e s s i o n E q u a t i o n s R e l a t i n g D i g e s t i b i l i t y o f Dry-

M a t te r t o t h e L i g n i n C o n te n t o f R a t i o n

R e g r e s s i o n E q u a t i o n C o r r e l C o e f f .

M a t e r i a l R e f e r e n c e

Y =93.9 - 3 .0 4 X - 0 .9 3 9 A l f a l f a P h i l l i p s and L o u g h l in ( 1 5 1 ) .

Y = 1 2 0 .3 - 5 . 9 6X - 0 . 9 5 4 T im othy P h i l l i p s and L o u g h l in ( 1 5 1 ) .

Y =84.9 - 1 .1 5 X — S u l p h i t e C e l l u l o se

H v i d s t e n ( 9 5 ) .

Y = 9 5 .9 - 4 .06X - 0 . 9 7 H o r d f e l d t e t a l . ( 1 3 2 ) .

Y=96.4- - 4 .4 4 X --------- F o r b e s and G a r r i g u s ( 7 0 ) .

Y=lOO - 4 . 7 IX - 0 . 9 5 S t e e r s ,P a s t u r e

F o r b e s and G a r r i g u s ( 7 1 ) .

Y=100 - 5 .2 4 X - 0 . 9 3 W e th e r s ,P a s t u r e

I t M it

Y=97 - 4 .3 3 X ——— B ro m e g ra ss P a s t u r e

t t it it

Y=100 - 5 .32X O r c h .G r a s s P a s t u r e

w « w

Y=96 - 4 .8 1 X ——— Ky.31 F e s c u e " " ,T P a s t u re

Y=100 - 4 . 9 2X —— A l f a l f a Pasture

ii t t m

Y=94- - 2 .9 5 X — — L a n c a s t e r ( 1 1 0 ) .

E f f e c t o f M e th o x y l C o n te n t o f P l a n t s on D i g e s t i b i l i t y

T h e re i s some i n d i c a t i o n t h a t c h a n g e s i n t h e l i g n i n m o le c u le o r i n i t s

d i s t r i b u t i o n t h r o u g h t h e c e l l w a l l may h av e m ore e f f e c t on d i g e s t i b i l i t y o f

o t h e r c o n s t i t u e n t s t h a n t h e q u a n t i t y o f l i g n i n p r e s e n t . M angold (1 1 5 ) and

Woodman an d S t e w a r t ( 1 9 0 , 1 9 1 ; h a v e shown t h a t t h e d e c r e a s e i n d i g e s t i b i l i t y

o f g r a s s e s w i t h i n c r e a s i n g m a t u r i t y m<ay be a c c o m p an ied b y r a t h e r s m a l l i n ­

c r e a s e s i n th© l i g n i n c o n t e n t . As p l a n t s m a t u r e , t h e l i g n i n c o n t e n t u s u ­

a l l y i n c r e a s e s and t h e r e i s a l s o an i n c r e a s e i n t h e m e th o x y l c o n t e n t o f

t h e l i g n i n . (136* 1 4 7 , 1 4 8 , 1 4 9 ; .

40

Francois e t a l . (75) found t h a t a p p r o x i m a t e l y 50 p e r c e n t o f t h e t o t a l

m e th o x y l c o n t e n t , 50 p e r c e n t o f t h e m e th o x y l c o n t e n t o f t h e l i g n i n , an d 90

p e r c e n t o f t h e m e th o x y l c o n t e n t o f t h e p e c t i n i n r a t i o n s f e d t o two c a l v e s

d i s a p p e a r e d , a s i n d i c a t e d f ro m a n a l y s i s o f t h e u r i n e and f e c e s * They u s e d

10 - d a y c o l l e c t i o n p e r i o d s on r a t i o n s c o n t a i n i n g a l f a l f a h a y a l o n e , a l f a l f a

p l u s d r i e d b e e t p u l p , a l f a l f a p l u s w h e a t , and a l f a l f a p l u s d r i e d b e e t p u l p

an d w h ea t* P h i l l i p s e t a l . ( 1 5 0 ) a n d C so n k a , P h i l l i p s and J o n e s ( 4 8 ) h a d

p r e v i o u s l y r e p o r t e d a 15 p e r c e n t l o s s o f m e th o x y l i n t h e d i g e s t i v e t r a c t

o f a dog an d a 37 p e r c e n t l o s s by a cow*

The m e th o x y l c o n t e n t o f g r a s s and f e c e s h a s b e e n r e p o r t e d by R e id

(1 5 3 ) t o show a h i g h n e g a t i v e c o r r e l a t i o n t o t h e t o t a l d i g e s t i b l e n u t r i ­

e n t s c o n t e n t o f t h e g r a s s * The c o r r e l a t i o n c o e f f i c i e n t s r e l a t i n g t h e

m e th o x y l c o n t e n t o f g r a s s w i t h t h e a p p a r e n t d i g e s t i o n c o e f f i c i e n t s o f

s e v e r a l c o n s t i t u e n t s o f t h e g r a s s a ro shown i n T ab le 6 .

T ab le 6 .

C o r r e l a t i o n o f M e th o x y l C o n te n t o f G ra s s w i t h t h e A p p a r e n t

D i g e s t i o n C o e f f i c i e n t s o f S e v e r a l G ra s s C o n s t i t u e n t s

C o n s t i t u e n to

C o r r e l a t i o n C o e f f i c i e n t ^

C e l l u l o s e -0 * 9 0 0

H e m i c e l l u l o s e s - 0 .8 9 6

C rude F i b e r - 0 .8 8 7

Pe c t i n s - 0 .8 6 5

S t a r c h - 0 . 9 2 1

C ru d e P r o t e i n - 0 . 9 3 3

T o t a l d i g e s t i b l e n u t r i e n t s - 0 . 9 6

^■From E e i d (1 5 3 )*

2A11 c o e f f i c i e n t s h i g h l y s i g n i f i c a n t .

41

R e id ( 1 5 3 ) a l s o p o i n t e d o u t t h a t t h e m e th o x y l c o n t e n t o f g r a s s c u t a t

a l a t e s t a g e h a d i n c r e a s e d 32*9 p e r c e n t i n m e th o x y l c o n t e n t o v e r t h a t w h ic h

i t c o n t a i n e d when c u t a t an e a r l y s t a g e *

P h i l l i p s an d Goss ( 1 4 8 ) h a v e shown t h a t t h e m e th o x y l c o n t e n t o f p l a n t s

i s n o t e n t i r e l y a s s o c i a t e d w i t h t h e l i g n i n m o le c u le an d t h e p r o p o r t i o n o f

t h e t o t a l am ount w h ic h i s a s s o c i a t e d w i t h t h e l i g n in m o le c u le i n c r e a s e s

w i t h more m a tu r e p l a n t s *

E f f e c t o f S ta g e o f M a t u r i t y on D i g e s t i b i l i t y

S c i e n t i f i c w o r k e r s an d l i v e s t o c k f e e d e r s h a v e u n d o u b t e d l y b e e n aw are

o f t h e d i f f e r e n c e i n n u t r i t i v e v a l u e o f r o u g h a g e s h a r v e s t e d a t d i f f e r e n t

s t a g e s o f m a t u r i t y lo n g b e f o r e e x p e r i m e n t a l d a t a w e re c o l l e c t e d on t h i s

s u b j e c t * The p r i m a r y p u r p o s e o f t h i s s e c t i o n i s to r e v i e w t h o s e e x p e r i ­

m e n t s w h ic h i n v e s t i g a t e d c h a n g e s i n t h e d i g e s t i b i l i t y o f t h e d r y m a t t e r o f

f o r a g e s o r o f t h e v a r i o u s c o n s t i t u e n t s o f t h e d r y m a t t e r a n d w i l l n o t a t ­

t e m p t t o r e v i e w a l l o f t h e s t u d i e s w h ic h h a v e i n v e s t i g a t e d c h a n g e s i n

c h e m i c a l c o m p o s i t i o n w i t h v a r i o u s s t a g e s o f m a t u r i t y o f p l a n t s *

M i l l s (1 2 4 ) a n d F o s t e r and M e r r i l l ( 7 3 ) a t th e U ta h A g r i c u l t u r a l

E x p e r i m e n t S t a t i o n c u t a l f a l f a when t h e f i r s t b lo s s o m s a p p e a r e d , when i n

f u l l b loom , and w hen h a l f o f t h e b lo s s o m s h a d f a l l e n * They p r o d u c e d t h e

g r e a t e s t am o u n ts o f b e e f p e r u n i t o f h ay f r o m t h e e a r l i e s t s t a g e s and t h e

s m a l l e s t am o u n ts f ro m t h e m o s t m a tu r e s t a g e * The e a r l i e s t s t a g e a l s o c o n ­

t a i n e d t h e h i g h e s t am ount o f p r o t e i n * S a lm o n , S w anson and Me Camp be 11 (1 6 0 )

c u t a l f a l f a a t t h o b u d , o n e - t e n t h b lo o m , f u l l b loom a n d s e e d s t a g e s . The

a s h an d p r o t e i n c o n t e n t d e c r e a s e d a s t h e m a t u r i t y a d v a n c e d end th e c ru d e

f i b e r c o n t e n t i n c r e a s e d . S i x t y - t o n i n e t y - d a y f e e d i n g t e s t s c o n d u c te d f o r

t h e v a r i o u s c u t t i n g s on t h r o e d i f f e r e n t y e a r s w i t h s t e e r s o n t h e a l f a l f a

h a y w i t h o u t a n y o t h e r f e e d showed t h a t 1628 p o u n d s o f bud s t a g e hay p r o d u c e d

100 p o u n d s o f g a i n i n l i v e - w e i g h t a s com pered t o 2 ,0 8 6 p o u n d s o f o n e - t e n t h

b lo o m h a y , 2*163 p o u n d s o f f n l l - b l o o m h a y , and 3 ,9 1 0 p o u n d s o f s e e d - s t a g e

hay* D i g e s t i o n t r i a l s showed a n a v e r a g e d i g e s t i o n c o e f f i c i e n t o f 78 p e r ­

c e n t f o r t h e p r o t e i n i n h a y c u t a t t h e bud s t a g o , 73 p e r c e n t f o r t h a t i n

t h e o n e - t e n t h b loom an d f u l l - b l o o m h a y s , end 67 p e r c e n t f o r t h a t i n t h e

h a y c u t a t t h e s e e d s t a g e * The c r u d e f i b e r i n t h e bud s t a g e h a y s h a d an

a v e r a g e d i g e s t i o n c o e f f i c i e n t o f 35 p e r c e n t , a s com pared to an a v e r a g e o f

48 p e r c e n t f o r t h e o n e - t e n t h b lo o m , 43 p e r c e n t f o r t h e f u l l b loom , and 41

p e r c e n t f o r t h e s o e d - s t a g e h a y . Woodman, E v a n s and Norman ( 1 8 8 , 1 8 9 ) co n ­

d u c t e d d i g e s t i o n t r i a l s w i t h sh e e p on a l f a l f a c u t a t t h e p r e b u d , b u d , a n d

f l o w e r i n g s t a g e s . A l f a l f a c u t a t a p r e b u d s t a g e was s u p e r i o r t o l a t e r

c u t t i n g s and co m p ared f a v o r a b l y w i t h you n g p a s t u r e g r a s s i n n u t r i t i v e

v a lu e * They a l s o p o i n t e d o u t t h a t t h e a l f a l f a p l a n t p r o d u c e d f i b e r a t

an e a r l y s t a g e o f g ro w th a n d t h a t th e d i g e s t i b i l i t y o f t h e f i b e r d im in ­

i s h e d r a p i d l y a s a r e s u l t o f l i g n i f i c a t i o n * The a v e r a g e c r u d e p r o t e i n

c o n t e n t w as 2 8 .1 p e r c e n t f o r f i v e c u t t i n g s o f p re b u d h a y a s com pared t o

2 1 .5 and 19*3 p e r c e n t f o r t h e b u d s t a g e and b loom s t a g e c u t t i n g s , r e s p e c ­

t i v e l y . The c r u d e f i b e r c o n t e n t a v e r a g e d 1 9 . 3 p e r c e n t f o r t h © 'p r e b u d

s t a g e , i n c r e a s e d t o 2 6 .5 f o r t h e bud s t a g e , and 27 f o r t h e b loom s t a g e

h a y . The d i g e s t i o n c o e f f i c i e n t s w ere c o n s i d e r a b l y h i g h e r f o r h a y c u t i n

t h e p r e b u d s t a g e t h e n f o r t h e h a y s c u t a t th o l a t e r s t a g e s . The d i g e s t i o n

c o e f f i c i e n t s f o r c r u d e p r o t e i n a v e r a g e d 80 p e r c e n t f o r t h e p r c b u d s t a g e ,

78 p e r c e n t f o r t h e bud s t a g e , and 76 p e r c e n t f o r t h e b loom s t a g e h a y .

D i g e s t i o n c o e f f i c i e n t s f o r c ru d e f i b e r a v e r a g e d 6 4 , 48 a n d 43 f o r t h e

t h r e e s t a g e s , r e s p e c t i v e l y . S o t o l a (1 7 0 ) c u t i r r i g a t e d a l f a l f a h a y a t

o n e - f o u r t h , o n e - h a l f , and t h r e e - f o u r t h b looin s t a g e s . The p r o t e i n c o n t e n t

d e c r e a s e d and th e f i b e r c o n t e n t i n c r e a s e d a s th e p l a n t s m a tu r e d . The h a y

c u t a t t h e o n e - h a l f b loom s t a g e was h i g h e s t i n d i g e s t i b l e c r u d e p r o t e i n

43

a n d i n t o t a l d i g e s t i b l e n u t r i e n t s . The d i g e s t i o n t r i a l s o f h le w lan d er e t a l .

( 1 2 9 ) w i t h cows o n s u n - c u r e d a l f a l f a t h a t was c u t a t t h e o n e - h a l f b loom

s t a g e gave an a v e r a g e d i g e s t i o n c o e f f i c i e n t f o r c ru d e p r o t e i n o f 7 8 . 3 f o r

t h e n o - b lo o m a n d 6 5 .8 f o r t h e o n e - h a l f b loom h a y . The d i g e s t i o n c o e f f i c i e n t s

o f t h e n i t r o g e n - f r e e e x t r a c t com pared c l o s e l y f o r b o th h a y s , b u t c r u d e f i b e r

a v e r a g e d 5 5 .3 f o r t h e n o -b lo o m s t a g e and 5 3 .2 f o r t h e o n e - h a l f b lo o m h a y ,

The t o t a l d i g e s t i b l e n u t r i e n t c o n t e n t o f th e d r y m a t t e r a v e ra g e d 6 3 .3 p e r ­

c e n t f o r t h e n o -b lo o m h a y and. 5 8 . 3 p e r c e n t f o r t h e o n e - h a l f b loom h a y .

D aw son, K op lan d and G ra v e s ( 5 l ) r e p o r t e d t h e d i g e s t i b i l i t y o f a l f a l f a h a y

c u t i n t h r e e s t a g e s , a s f o l l o w s 5 ( 1 ) i n i t i a l b loom s t a g e , when n o t m ore t h a n

10 p e r c e n t o f t h e p l a n t s w e re i n b loom ; ( 2 ) o n e - h a l f b loom s t a g e ; and ( 3 )

f u l l b loom s t a g e , w hen 90 t o 100 p e r c e n t o f th e p l a n t s w e re i n b lo o m . D i­

g e s t i o n t r i a l s o f f i f t e e n - d a y s c o l l e c t i o n s w e re c o n d u c t e d w i t h s h e e p . The

a v e r a g e d i g e s t i o n c o e f f i c i e n t f o r t h e c r u d e p r o t e i n w as 7 7 .7 f o r t h e i n i t i a l

b loom h a y a s co m p ared t o 7 7 .1 f o r th e o n e - h a l f b loom and 7 5 .4 f o r th e f u l l

b lo o m h a y . The d i g e s t i o n c o e f f i c i e n t s f o r th e c r u d e f i b e r a v e r a g e d 4 7 .7

f o r t h e i n i t i a l b lo o m , 4 1 . 4 f o r t h e o n e - h a l f b loom , and 3 8 .3 f o r f u l l b loom

h a y . The t o t a l d i g e s t i b l e n u t r i e n t s o f t h e d r y m a t t e r was 5 9 .0 p e r c e n t f o r

t h e i n i t i a l b lo o m , 5 6 .7 f o r t h e o n e - h a l f b lo o m , and 5 3 .9 f o r th e f u l l b loom

h a y ,

S o t o l a (1 7 1 ) h a s shown t h a t t h e d i g e s t i b i l i t y o f w h e a t and b a r l e y p l a n t s

d o e s n o t d e c r e a s e p r o g r e s s i v e l y w ith , a d v a n c in g m a t u r i t y s i n c e t h e m i l k and

d o u g h s t a g e s o f t h e g r a i n f o r m a t i o n y i e l d h i g h l y d i g e s t i b l e n u t r i e n t s t h a t

l a t e r d e c r e a s e i n d i g e s t i b i l i t y d u e to m a t u r a t i o n o f t h e v e g e t a t i v e p a r t o f

t h e p l a n t . S o t o l a ( 1 7 2 ) a l s o com pared t h e d i g e s t i o n c o e f f i c i e n t s f o r c r e s t e d

w h e a t g r a s s c l i p p e d a t f o u r - i n c h a rd t e n - i n c h h e i g h t s . The c o e f f i c i e n t s o f

a p p a r e n t d i g e s t i b i l i t y f o r th e f b u r - i n c h and t e n - i n c h c u t t i n g s w o re ; d r y

m a t t e r , 6 6 .7 and 6 G .7 ; c r u d e p r o t e i n , 7 4 .3 and 5 9 . 7 ; c r u d e f i b e r , S 3 .5 and

44

6 7 . 85 and n i t r o g e n - f r e e e x t r a c t , 7 4 .5 and 7 4 . 8 , r e s p e c t i v e l y . T h i s com­

p a r i s o n i l l u s t r a t e s t h e v a l u e o f a c o m p a r i s o n o f t h e d i g e s t i b i l i t y o f t h e

v a r i o u s c o n s t i t u e n t s i n c o n t r a s t t o a c o m p a r i s o n o±* o n l y t h e d r y m a t t e r

d i g e s t i b i l i t i e s i n a p a s t u r e e v a l u a t i o n s t u d y . S o t o l a (1 7 3 ) s t u d i e d

c h a n g e s i n c h e m ic a l c o m p o s i t i o n and a p p a r e n t d i g e s t i b i l i t y o f n u t r i e n t s

i n sm o o th brome g r a s s c u t a t r e g u l a r i n t e r v a l s d u r i n g t h e g ro w in g s e a s o n .

The c r u d e p r o t e i n d e c r e a s e d f ro m 1 3 .6 t o 4 . 0 p e r c e n t 'w h ile t h e c r u d e f i b e r

i n c r e a s e d f ro m 1 9 .8 t o 3 5 .9 p e r c e n t d u r i n g g ro w th o f t h e p l a n t s f ro m 4 . 5

t o 36 i n c h e s i n h e i g h t . The d r y m a t t e r was 81 p e r c e n t d i g e s t i b l e a t t h e

f o u r - and t e n - i n c h s t a g e s an d o n l y 5 5 .8 p e r c e n t d i g e s t i b l e a t t h e 3 6 - i n c h

s t a g e . D i g e s t i b i l i t y o f t h e c r u d e p r o t e i n , c r u d e f i b e r and n i t r o g e n - f r e e

e x t r a c t f o l l o w e d s i m i l a r t r e n d s .

The d i g e s t i b i l i t y o f a m i x t u r e o f v e l d g r a s s e s c u t a f t e r p e r i o d s o f

1 , 2 , 3 and 4 m o n th s g ro w th m s s t u d i e d by Louw ( 1 1 3 ) . W ith i n c r e a s i n g

m a t u r i t y o f t h e g r a s s t h e p e r c e n t a g e o f n a t u r a l c e l l u l o s e and t h e r a t i o o f

x y l a n to t r u e c e l l u l o s e i n c r e a s e d s l i g h t l y . The i n c r e a s e i n . th e l i g n i n an d

h e m i c e l l u l o s e c o n t e n t s w e re r e l a t i v e l y s m a l l . The d i g e s t i b i l i t y o f c e l l u ­

l o s e , p e n t o s a n s and h e m i c e l l u l o s e a l l d e c r e a s e d w i t h a d v a n c in g m a t u r i t y .

D i j k s t r a and B rouw er (5 4 ) r e p o r t e d on c h a n g e s i n c h e m ic a l c o m p o s i t i o n and

f e e d i n g v a l u e o f g r a s s mowed a t d i f f e r e n t s t a g e s o f m a t u r i t y . 7sri t h i n ­

c r e a s i n g age o f t h e g r a s s t h e p e r c e n t a g e o f p r o t e i n d e c r e a s e d and t h e p e r ­

c e n t a g e o f c e l l u l o s e i n c r e a s e d . D i g e s t i b i l i t y and f e e d i n g v a l u e d e c r e a s e d

w i t h i n c r e a s i n g m a t u r i t y . T hey a l s o r e p o r t e d t h e d i g e s t i b i l i t y o f t h e

c r u d e c e l l u l o s e a s n o t a p p r e c i a b l y d i f f e r e n t f ro m t h e s t a r c h i n d i g e s t i o n

t r i a l s w i t h s h e e p . B u r k i t t ( 2 7 ) c o n d u c te d d i g e s t i b i l i t y t r i a l s w i t h sh e e p

o n b e a r d l e s s w h e a t g r a s s c u t a t a n e a r l y (3 t o 5 i n c h e s ) , medium (7 t o 10

i n c h e s ) and l a t e stage- o f g r o w th . The c o e f f i c i e n t o f a p p a r e n t d i g e s t i b i l ­

i t y o f a l l t h e v a r i o u s n u t r i e n t s d ro p p e d a s th e g r a s s m a tu r e d . Sw anson

45

a n d H erm an (1 7 6 ) fo u n d t h e d i g e s t i b i l i t y o f p r a c t i c a l l y a l l t h e n u t r i e n t s

o f K o re a n l e s p e d e z a h a y d e c r e a s e d w i t h a d v a n c in g m a t u r i t y and i n c r e a s i n g

l i g n i n c o n t e n t * The d i g e s t i b i l i t y t r i a l s "were c o n d u c t e d w i t h d a i r y h e i f e r s *

U nderwood and M o ir (1 8 0 ) c o n d u c t e d d i g e s t i o n t r i a l s w i t h s h e e p on w h e a t

an d o a t h a y c u t a t v a r i o u s p e r i o d s o f g ro w th r a n g i n g f ro m b e f o r e f l o w e r i n g

t o w hen t h e g r a i n w as p r a c t i c a l l y m a tu re * The f i r s t c u t t i n g o f w h e a t h a y

h a d t h e h i g h e s t d i g e s t i o n c o e f f i c i e n t f o r a l l c o n s t i t u e n t s , e x c e p t t h e

e t h e r e x t r a c t * The c r u d e p r o t e i n and f i b e r h a d d e c i d e d l y lo w e r d i g e s t i o n

c o e f f i c i e n t s i n t h e l a t e r c u t t i n g s o f b o t h t h e w h e a t and o a t h a y , A d e c l i n e

i n t h e d i g e s t i b i l i t y o f p a s t u r e h e r b a g e d r y m a t t e r f r o m a b o u t 75 p e r c e n t

f o r e a r l y s p r i n g g r a s s t o 60 p e r c e n t a b o u t s i x w eek s l a t e r was r e p o r t e d

by C ram p to n and J a c k s o n ( 4 4 ) . D r a p a l a , Raymond and Cram pton ( 5 5 ) made

h i s t o l o g i c a l e x a m i n a t i o n s o f t h e p l a n t r e s i d u e s i s o l a t e d f ro m t h e f e c e s

o f s h e e p on c l o v e r c u t a t v a r i o u s s t a g e s o f m a t u r i t y and fo u n d t h e i n c r e a s e

i n t h e num ber o f u n d i g e s t e d b i t s o f p l a n t t i s s u e s i n t h e f e c e s and t h e i r

i n c r e a s e i n s i z e was c o r r e l a t e d w i t h t h e i n c r e a s e i n m a t u r i t y o f t h e f o r ­

a g e e a t e n and i t s i n c r e a s i n g l i g n i f i c a t i o n * D e c r e a s e s i n d i g e s t i b i l i t y

h a v e b e e n shown t o b© a s s o c i a t e d w i t h a d v a n c in g m a t u r i t y i n f l a t p e a f o r -

b y D a n i e l e t a l . ( 4 9 ) , t i m o t h y h ay b y C o lo v o s e t a l* ( 3 8 ) , and pam pas

g r a s s by D un lop an d Coup ( 5 8 ) . R e id (1 5 5 ) h a s a l s o r e c e n t l y r e p o r t e d

t h a t t h e d i g e s t i o n c o e f f i c i e n t s o f t h e d r y m a t t e r o f e a r l y , medium and

l a t e c u t g r a s s w as 7 2 * 2 , 66*6 and 5 6 . 0 , r e s p e c t i v e l y .

E f f e c t o f P l a n t Ash on D i g e s t i b i l i t y .

B u r ro u g h s e t a l . (3 o ) f i r s t p r e s e n t e d e v i d e n c e w h ic h i n d i c a t e d t h e

p r e s e n c e o f n u t r i e n t s i n a l f a l f a hey t h a t h a d a f a v o r a b l e i n f l u e n c e on

t h e d i g e s t i b i l i t y o f a p o o r q u a l i t y ro u g h a g e when f e d t o c a t t l e . T h e i r

p r e v i o u s e x p e r i e n c e ( 3 2 ) i n f i n d i n g t h a t c o r n s t a r c h e x e r t e d l i t t l e o r no

46

e f f e c t u pon t h e d i g e s t i b i l i t y o f t h e d r y m a tb e r o f good q u a l i t y a l f a l f a

h a y ; h u t when a d d e d t o a p o o r q u a l i t y ro u g h a g e ( c o r n c o b s ) , t h e c o r n s t a r c h

c a u s e d a m a rk e d d e c r e a s e m t h e d i g e s t i b i l i t y o f t h e ro u g h a g e d r y m a t t e r *

T h e s e r e s u l t s i n d i c a t e d t h a t a l f a l f a h a y c o n t a i n e d c e r t a i n n o n - p r o t e i n

m a t e r i a l e s s e n t i a l f o r t h e g ro w th o f rum en m ic r o o r g a n is m s n e c e s s a r y f o r

ro u g h a g e d i g e s t i o n s i n c e a p p r o x i m a t e l y t h e same am oun ts o f p r o t e i n w ere

f e d w i t h e a c h o f t h e r o u g h a g e s s tu d i e d * They f e l t t h a t i f a ro u g h a g e i s

f e d w i t h s t a r c h t h e d i g e s t i b i l i t y w i l l n o t be lo w e re d i f t h e r e i s a s u f f i ­

c i e n t ©mount o f t h e unknown n u t r i e n t s t o s u p p ly t h e r e q u i r e m e n t s o f m i c r o ­

o r g a n i s m s s u b s i s t i n g o n b o t h t h e s t a r c h and t h e r o u g h a g e , h o w e v e r , i f

s u f f i c i e n t q u a n t i t i e s o f t h e s e n u t r i e n t s a r e n o t p r e s e n t i n t h e r o u g h a g e ,

t h e s t a r c h w i l l d e c r e a s e t h e d i g e s t i b i l i t y o f t h e ro u g h a g e s i n c e t h e m i c r o ­

o r g a n i s m s a t t a c k i n g s t a r c h w i l l d e p l e t e t h e ro u g h a g e o f n u t r i e n t s n e e d e d

f o r t h e a p p a r e n t l y s lo w e r a c t i n g m ic r o o r g a n i s m s c o n c e rn e d i n ro u g h a g e d i ­

g e s t i o n j» B u r ro u g h s e t a l . ( 3 5 ) r e p o r t e d a s e r i e s o f t h r e e d i g e s t i o n t r i a l s

u s i n g g r a d e H e r e f o r d s t e e r s a s f o l l o w s j ( 1 ) d i g e s t i o n o f c o r n c o b s i n

r a t i o n s c o n t a i n i n g ■ v a r ia b le am ounts o f h a y , (2 ) d i g e s t i o n o f c o r n c o b s i n

r a t i o n s w i t h and w i t h o u t a d d i t i o n s o f a w a te r e x t r a c t o f a l f a l f a h a y , and

( 3 ) t h e i n f l u e n c e o f a l f a l f a a s h u p o n c o rn c o b d i g e s t i o n . I n t h e f i r s t

s e r i e s e a c h i n c r e m e n t o f a l f a l f a h a y ( 0 . 5 t o 5 .0 p o u n d ) i n t h e r e s p e c t i v e

r a t i o n s r e s u l t e d i n i n c r e a s e d d i g e s t i o n o f c o r n c o b s . S i m i l a r e f f e c t s w e re

s e c u r e d w i t h t h e a d d i t i o n o f a w a t e r e x t r a c t o f a l f a l f a t o t h e r a t i o n a l ­

th o u g h t h e r e s p o n s e w as q u i t e s low and th e i n c r e a s e d d i g e s t i b i l i t y c o n ­

t i n u e d f o r a s h o r t t im e a f t e r remove 1 o f th e w a t e r e x t r a c t o f a l f a l f a .

The a d d i t i o n o f a l f a l f a a s h a p p r o x i m a t e l y e q u i v a l e n t t o t h a t fo u n d I n

f o u r p o u n d s o f a l f a l f a m e a l was f e d t o e a c h o f f o u r s t e e r s i n two d i g e s ­

t i o n t r i a l s . The a d d i t i o n o f t h e a l f a l f a a sh I n c r e a s e d t h e d i g e s t i b i l i t y

47

o f th e dry matter from 31 .6 percent in the con tro l period to 43.5 percent

in the supplemented period*

S w ift e t a l * (177) extended the work reported by Burroughs (33) to

a comparison o f the m etabolizable energy and methane production o f sheep

fed a basal ra tio n containing 40 percent ground com cobs and the basal

ra tion p lu s a l f a l f a ash* They reasoned th a t an increase in the apparent

d ig e s t ib i l i t y o f dry matter and crude fib er would be o f no value to the

animal i f th ere was an increase in methane production corresponding to

the decrease in fe c a l output* The d ig e s t ib i l i t y of a l l o f the ra tio n

c o n stitu e n ts was increased by a l f a l f a ash supplem entation, but the increase

in the d i g e s t i b i l i t y o f crude f ib e r was the only one found to be h igh ly

s ig n if ica n t* The increase in the crude fib er d ig e s t ib i l i t y was accom­

panied by a small in crease in methane production which was small enough

th at the n e t e f f e c t o f a l f a lf a ash supplementation was to increase the

amount o f feed energy ava ilab le to the animal.

A ssoc ia tive E ffec t o f Feeds and D ig e s t ib i l i t y

A sso c ia tiv e d ig e s t ib i l i t y i s the term applied to a change in the

d ig e s t ib i l i t y o f a feed when incorporated in a ra tion w ith one or more

other feed s as compared to i t s d ig e s t ib i l i t y when fed alone* Ewing and

YSells (65) were apparently the f i r s t to use the term, " assoc ia tive d ig e s t ­

i b i l i t y ”, when they studied mixed ration s composed o f corn s i la g e , cotton ­

seed m eal, and starch . The c o e f f ic ie n ts o f d ig e s t ib i l i t y for the cotton­

seed meal ca lcu la ted from the mixed ration with s ila g e were higher than

the va lu es for cotton seed meal fed a lone, but the d ifferen ces were report­

ed to be not s ig n if ic a n t . They la te r (64) in v estig a ted ration s composed

o f com s i la g e , a l f a l f a , and v e lv e t bean meal in various combinations and

prop ortion s. In the s ila g e and a l f a l f a r a tio n , s ila g e and v e lv e t bean

m e a l r a t i o n , v e l v e t b e a n m e a l and a l f a l f a r a t i o n , and t h e s i l a g e , a l f a l f a

and v e l v e t b e a n m e a l r a t i o n , t h e c o e f f i c i e n t s o f d i g e s t i b i l i t y o f t h e d r y

m a t t e r , n i t r o g e n , c r u d e f i b e r , and n i t r o g e n - f r e e e x t r a c t o f t h e m ixed

r a t i o n s w ere l e s s t h a n th e v a l u e s c a l c u l a t e d f ro m th e c o e f f i c i e n t s o f t h e

i n d i v i d u a l com ponen ts# The d i f f e r e n c e s w e re o n l y tw o t o f o u r a b s o l u t e p e r ­

c e n t#

W atson e t a l . (1 8 4 ) s t u d i e d t h e a s s o c i a t i v e d i g e s t i b i l i t y o f d r y and

s u c c u l e n t ro u g h a g e s u c h a s m ixed h a y , o a t s t r a w , o a t h u l l s , c o r n s i l a g e ,

an d m a n g e ls when f e d t o s t e e r s * The c o e f f i c i e n t s o f d i g e s t i b i l i t y we r e

d e t e r m i n e d w hen t h e s e f e e d s w ere f e d a s t h e s o l e r a t i o n and when c o m b in a ­

t i o n s o f v a r i o u s p a i r s o f t h e s e f e e d s made up th e r a t i o n . The d i g e s t i b i l i t y

o f o n e o f t h e I n d i v i d u a l co m p o n en ts i n e a c h m ixed r a t i o n was t h e n com pared

w i t h i t s d i g e s t i b i l i t y when f e d a l o n e . T hey c o n c lu d e d t h a t among m ixed

h a y , o a t s t r a w , c o r n s i l a g e and m a n g e ls t h e r e was 110 a s s o c i a t i v e e f f e c t

o n t o t a l d i g e s t i b i l i t y o r t o t a l d i g e s t i b l e n u t r i e n t s . They a l s o c o n c lu d e d

t h a t t h e d i g e s t i b i l i t y o f o a t h u l l s , c a l c u l a t e d f ro m a m ixed r a t i o n w i t h

e i t h e r h a y , c o r n s i l a g e , o r m a n g e l s , was lo w e r t h a n t h e d i g e s t i b i l i t y o b ­

s e r v e d w hen o a t h u l l s c o n s t i t u t e d t h e s o l e r a t i o n , h fa tso n e t a l « (1 8 5 )

d e t e r m i n e d t h e d i g e s t i o n c o e f f i c i e n t s o f b a r l e y , o a t s , o i l c a k e , b a r l e y

p l u s o a t s , and b a r l e y p l u s o a t s and o i l c a k e i n a b a s a l r a t i o n o f h ay by

u s i n g s t e e r s . They c o n c lu d e d t h a t t h e r e was no a s s o c i a t i v e e f f e c t b e tw e e n

b a r l e y and o a t s and o n l y s l i g h t l y h i g h e r d i g e s t i b i l i t i e s o f t h e d r y m a t t e r

o f t h e b a r l e y p l u s o a t s and o i l cake r a t i o n w ere found e x p e r i m e n t a l l y t h s n

w e re c a l c u l a t e d . U s in g r a t i o n s o f b a r l e y , o a t s and o i l c ak e a l o n e and

a l s o when t h e y w e re f e d i n a m ix ed r a t i o n w i t h h a y , W atso n e t a l , (1 8 2 )

r e p o r t e d on t h e a s s o c i a t i v e d i g e s t i b i l i t y o f h a y and t h o s e g r a i n s # ; i t h

o i l c a k e t h e r e w ere no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s b e tw e e n t h e

v a l u e s o b t a i n e d by c a l c u l a t i o n f ro m t h e m ixed r a t i o n and t h o s e o b t a i n e d

when t h e o i l c a k e c o n s t i t u t e d t h e e n t i r e r a t i o n * T h e re w ere a l s o no s t a ­

t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s i n t h e c a s e o f b a r l e y , e x c e p t f o r t h e

e t h e r e x t r a c t * The d i g e s t i b i l i t y o f t h e e t h e r e x t r a c t , c a l c u l a t e d f ro m

t h e m ixed r a t i o n w i t h h a y , was h i g h e r t h a n t h a t d e t e r m in e d by f e e d i n g t h e

b a r l e y a lo n e * W ith o a t s , e x c e p t f o r n i t r o g e n and e t h e r e x t r a . c t , t h e v a l u e s

c a l c u l a t e d f r o m t h e m ixed r a t i o n w i t h h ay w ere s i g n i f i c a n t l y l e s s t h a n t h e

v a l u e s o b t a i n e d when t h e o a t s w ere f e d a l o n e . F o r a l l t h r e e f e e d s , w i t h

t h e e x c e p t io n - o f e t h e r e x t r a c t , t h e v a l u e s c a l c u l a t e d f ro m m ix ed r a t i o n s

w i t h h a y t e n d e d t o be lo w e r t h a n t h e v a l u e s o b t a i n e d by f e e d i n g t h e g r a i n s

a lo n e * I t w as o n l y i n t h e c a s e o f o a t s t h a t s u c h d i f f e r e n c e s w ere s i g n i f ­

i c a n t * ' t f a t so n ert a l » ( 1 8 3 ) a l s o d e t e r m i n e d t h e c o e f f i c i e n t s o f d i g e s t i b i l ­

i t y f o r w h e a t b r a n , g l u t e n f e e d , so y b e a n o i l m e a l , end a m i x t u r e c o n s i s t i n g

o f e q u a l p a r t s o f t h e s e g r a i n s . From t h e v a l u e s o f t h e i n d i v i d u a l g r a i n s

a c a l c u l a t i o n was made o f t h e c o e f f i c i e n t s o f d i g e s t i b i l i t y o f t h e g r a i n

m i x t u r e w h ic h w as p r a c t i c a l l y I d e n t i c a l w i t h t h e v a l u e s d e t e r m in e d by

d i g e s t i b i l i t y t r i a l s . They c o n c lu d e d t h a t t h e r e was no a s s o c i a t i v e d i ­

g e s t i b i l i t y b e tw e e n t h e s e t h r e e g r a i n s . y ;a tso n e t a l . (1 8 6 ) r e p o r t e d on

t h e r e l a t i v e a s s o c i a t i v e e f f e c t s o f t i m o t h y said a l f a l f a , h a y s w i t h b a r l e y

w hen u s i n g s t e e r s and s h e e p and r a t i o n s o f b a r l e y , t i m o t h y h a y , a l f a l f a ,

h a y and m ix ed r a t i o n s o f b a r l e y p l u s t i m o t h y and. b a r l e y p l u s a l f a l f a . The

d i g e s t i b i l i t y o f b a r l e y w hen I t was f e d a lo n o was com pared w i t h th e d i ­

g e s t i b i l i t y when c a l c u l a t e d f ro m t h e b a r l e y p l u s t i m o t h y r a t i o n and t h e

b a r l e y p l u s a l f a l f a r a t i o n . The d i g e s t i b i l i t y o f b a r l e y w as t h e same

when f e d w i t h t i m o t h y , when f e d w i t h a l f a l f a o r w hen f e d a l o n e to sh eep

and s t e e r s .

S w i f t e t a l . (1 7 8 ) s t u d i e d t h e e f f e c t o f v a r i o u s s u p p le m e n t s on t h e

d i g e s t i b i l i t y o f a m ixed r a t i o n f o r s h e e p , h o w e v e r , o a t s t r a w was t h e

50

only natural feed supplement used* The add ition of crude f ib e r to the ra­

t io n in the fonn o f ©at straw reduced th e to t a l amount o f p ro te in and ether

e x tr a c t digested*

Graves e t a l * (82) did not conduct d ig e st io n t r i a l s in connection w ith

th e ir experim ents, but reported what appeared to be very l i t t l e d ifferen ce

in e f f ic ie n c y for m ilk production o f the to ta l d ig e s t ib le n u tr ien ts derived

from the a l f a lf a and th a t derived from the grain , hay, and s ila g e ration*

F ifte e n H olste in cows were kept on a l f a l f a hay alone for two or three la c ­

ta t io n s and although the cows were unable to consume as much t o t a l d ig e s t­

ib le n u tr ien ts as in a hay and grain r a tio n , they were able to . u t i l i z e the

n u tr ie n ts consumed w ith about th e same e ff ic ie n c y *

E ffe c t o f A n tib io tic s on D ig e s t ib i l i t y

Many recent reports have shown increased gains and accelerated growth

o f severa l sp ec ies o f animals rece iv in g various a n t ib io t ic supplements*

Some of th ese experim ents tend to in d ica te th a t a more e f f i c ie n t u t i l i z a ­

t io n o f n u tr ie n ts by the animal are responsib le fo r the increased growth

or w eight ga in s, but sin ce d ig e s t ib i l i t y comparisons w ith and w ithout

th ese supplements have not been made these experiments w i l l not be re­

viewed* Several experiments w ith d if fe r e n t sp ec ies o f animals have shown

th a t c e r ta in a n t ib io t ic s have a pronounced e f f e c t on the microorganisms

in the in t e s t in a l t r a c t . Since the ruminant is prim arily dependent upon

an a c tiv e m icrob ia l f lo r a for e f f i c ie n t d ig e stio n o f cer ta in feed con­

s t i tu e n t s , i t seems reasonable th a t a n t ib io t ic s might a f fe c t the d ig e s t­

i b i l i t y o f th ese n u tr ien ts depending upon the groups o f organisms th a t

were most g rea tly a ffec ted by th e a n t ib io t ic m aterial used.

B e ll , Hfhitehair and Gallup (20 ,21 ) studied the d ig e s t ib i l i t y o f a

basal ra tio n o f p ra ir ie hay, co m , soybean o i l m eal, bonemeal and s a l t

51

w ith "three steers* The same basal r a tio n p lu s 0*2 gram ©f c r y s ta ll in e

aureomycin hydrochloride was fed to th ree ad d ition a l s te e r s , one rece iv in g

only aureomycin and tw® 45 grams urea plus aureomycin* The s te e r s were

kept in metabolism s t a l l s and fed a constant amount of ra tion during a

ten -day prelim inary and a f if te e n -d a y c o lle c t io n period* The th ird day

a fter aureomycin feed in g was started two steers developed m ild anorexia

and diarrhea* About the f i f t h day a l l three s te e r s became s l ig h t ly con­

stip a ted w ith symptoms o f b loa t and th e ir fe c e s became dry and fibrous*

The e f f e c t o f aureomycin on the d ig e s t ib i l i t y of various feed co n stitu en ts

by s te e r s i s i l lu s tr a te d by m ateria l in Table 7 taken from the data of

B e ll e t a l . (2 1 ) .

52

T ab le 7 .

E ffe c t o f Aureomycin on D igestion C o e ffic ie n ts -with Steers^"

Percent Apparent D ig e s t ib i l i t y

Steer 5-Day Dry Crude Ether Crude N-FreeNo, Period Matter P rotein E xt. Fiber Ext.

z — -------- -------- ---------- ------- ------- --------and (Basal Ration)5

3—

1and6

1 69.07 51.93 63.31 66.35 74.91

2 66 . 58 52.68 58.38 62.77 74.93

3 70.69 55.42 65.94 67.01 76.20

4 69.57 55.15 66.93 65.45 75.40

5 72.67 60.83 71.52 70.60 77.96

Av. 70.04 53.20 65.26 66.44 75.88

(Basal Ration + Aureomycin)

1 76.36 65.64 74.63 66.29 81.86

2 63.71 56.27 62.76 49.71 70.48

3 58.00 47.60 66.51 55.88 67.25

4 54.06 45.31 60.50 30.72 65. 49

(B asal Ration + Urea * Aureomycin)

1 74.58 72.10 71.58 69.98 79.65

2 66.23 67.46 62.77 52.70 73.52

3 63.84 65.05 65.44 51.37 70.20

4 59.53 68.42 67.57 39.78 66.79

5 59.58 67.86 65.13 42.86 66.89

^From B e ll e t a l . (2 1 ) .

I t appears th a t the most pronounced e f f e c t of aureongrcSn was on the

d i g e s t i b i l i t y o f crude f ib e r which might suggest th a t i t had a detrim ental

53

®ff®ot "th.® c e l lu lo s e d ig e s t in g microorganisms of* the in te s t in a l tract*

The d ig e s t ib i l i t y o f the dry matter and crude f ib e r o f the ra tio n s was

markedly reduced in the la t t e r part o f the experiment*

SUMMARY OF THE REVIEW OF LITERATURE

D ig estio n t r ia l s involv ing the to ta l c o lle c t io n of fe c e s during a

te n day period o f constant feed intake have become a standard method for

determ ining the d ig e s t ib i l i t y o f various feeds*

Several in e r t m ater ia ls have been proposed and studied as a means o f

conducting d ig e s t io n t r i a l s by the so -c a lle d in e r t m ateria ls "ratio tech ­

nique”. A s a t is fa c to r y in e r t m aterial should be f u l ly recoverable in the

fe c e s and should have a n a ly t ic a l methods ava ilab le th at are e a s i ly con­

ducted and accurate. In some in stan ces i t would be h igh ly d esirab le to

have the in e r t m ateria l a n a tu ra lly occurring co n stitu en t o f -the p lan t

being studied*

Chromium, iro n , s i l i c a , l ig n in , in d ig e s t ib le n itrogen , cer ta in p lan t

pigments and various sy n th etic dyes have been proposed and studied as

in e r t m ater ia ls for use in the r a tio technique for d ig e s t ib i l i t y s tu d ie s .

C ontroversial r e s u lts have been reported w ith each o f these m ater ia ls

th a t have been studied by independent workers. Chromic oxide has given

s a t is fa c to r y r e s u lts fo r several in v e s t ig a to r s . 33ie method o f preparing

ft-na feed ing the chromium may be an important factor in i t s su ccessfu l

use as an in e r t m ateria l w ith ruminants. Wide ranges in the recover ies

o f l ig n in have been reported fo r various feeds Then fed to d if fe r e n t

animals and when the l ig n in analyses were made by d if fe r e n t methods.

The su ccessfu l use o f l ig n in as an in e r t m aterial depends upon a pre­

v iou s knowledge o f i t s recovery from the feed in question and w ith the

animal sp e c ie s in vo lved . D igestion c o e f f ic ie n t s ca lcu la ted from iron

54

r a t io s have bean h ig h ly var iab le and in some cases iron recoveries have

been very low* U n satisfactory r e s u lt s with the s i l i c a r a tio technique

have been reported when using the n a tu ra lly contained feed s i l i c a and a lso

when using added amounts o f s i l ic a * A n atu ra lly occurring plant pigment

or groups o f pigments have been reported which are fu l ly recoverable in

th e fe c e s and have a lso given sa t is fa c to r y r e s u lt s when used as an in e r t

m ateria l in d ig e s t ib i l i t y t r i a l s w ith severa l forages* Only lim ited com­

parisons have been reported w ith th e p lan t pigment r a tio technique o f

studying d ig e s t ib i l i t y * Further stu d ies o f syn th etic dyes are necessary

to evalu ate th e ir u se fu ln ess in d ig e s t ib i l i t y studies* Wo stu d ies have

been reported in which more than two in e r t m ater ia ls have been studied

in the same d ig e st io n t r i a l using the same feed and the same animals*

L ignin , crude f ib e r and c e l lu lo s e a l l show high negative c o rre la tio n s

w ith the d ig e s t ib i l i t y o f the dry matter o f feeds* A nalysis o f feed s for

th e ir conten t o f crude f ib e r has been c r it ic iz e d because ih e crude f ib e r

i s not o f uniform com position -when iso la te d from d iffe r e n t feed s and the

d is tr ib u tio n o f the various c o n stitu en ts between the crude f ib e r and

n itro g en -free e x tr a c t fr a c t io n s v a r ie s w idely w ith d if fe r e n t feeds*

PLAN OF EXPERIMENT AND METHODS USED

This study was planned to make a comparison of the d ig e st io n co­

e f f i c ie n t s determined with m ilking dairy cows fed orchard grass hay cu t

a t four sta g es o f m aturity ty the fo llow in g d ig e stio n t r i a l techniques:

(1 ) Total f e c a l c o lle c t io n technique*

(2 ) Chromium r a tio technique ( t o t a l c o lle c t io n )*

(3) P lan t pigment r a tio technique ( to t a l c o lle c t io n )*

(4 ) L ignin r a t io technique ( t o t a l c o lle c t io n )*

(5 ) Chromium r a tio technique (Grab samples)*

( 6 ) P lant pigment r a tio technique (Grab samples)*

55

The orchard grass hay used in t h is study urns cu t from a second growth

th a t had been p rev iou sly sprayed w ith 2,4-D for the contro l o f weeds end

c lo v e r . Ammonium sulphate was applied a t the rate o f 100 and 150 pounds

per acre approxim ately one month and one week r e sp e c tiv e ly , before the

f i r s t experim ental cu ttin g was made* The d if fe r e n t stages o f m aturity

were harvested a t approximately two week in te r v a ls as fo llow s:

Stage 1 6 to 7 inches high* (Pasture Stage) Cut May 19, 1949.

Stage 2 8 to 10 inches higjh* (Late pasture) Cut May 51, 1949.

Stage 3 10 to 12 inches high* (Early hay) Cut June 14, 1949.

Stage 4 12 to 14 inches high* (Mature Hay) Cut June 27, 1949.

The f i r s t cu ttin g was cu t in the f i e l d with a forage f i e l d chopper

and the chopped m ater ia l blown d ir e o t ly in to wagons and hauled to the

bam for a r t i f i c i a l drying. The la s t th ree cu ttin g s were l e f t in the

f i e l d fo r approxim ately one day and then windrowed w ith a sid e d e liv ery

rake and chopped from the windrow w ith a forage f i e Id-chopper* A ll lo t s

were dried on a s la t te d f lo o r bam d r ier w ith supplemental h ea t. After

drying, each l o t o f hay was baled and stored u n t i l fed .

D igestion t r i a l s were conducted on each lo t o f hay using three m ilk­

in g cows in d ig e s t io n s t a l l s th a t perm itted mechanical separation o f the

fe c e s and urine* Ten day prelim inary periods and ten day experim ental

periods were used fo r each lo t o f orchard grass stu d ied . The animals

were kept in th e d ig e st io n s t a l l s during the e n tir e prelim inary and

experim ental periods except for a d a ily period o f walking for e x e r c ise .

The feed in g schedule for the various stages o f orchard grass hay fed i s

given in Table 8 and the com position o f th e grain mixture fed i s given

in Table 9 .

56

Table 8 .

Animals used and q u a n tit ie s o f feed fed during the d ig e st io n t r i a l s

Animal Orchard grass hay No. 86 grain

X54 * 20 lbs* 7 lb s .

X65 ** 25 lb s . 5 lb s .

2408 26 lb s . 9 lb s .

N635 16 lb s . 7 lb s .

* Used w ith stage 4 hay on ly .

** Not used w ith stage 4 hay.

Table 9.

Composition o f No. 86 Grain Mixture

Ground Corn 97 p a r ts .

Bone meal 2 p a rts .

S a lt 1 p a r t.

Chromium oxide was added to the grain mixture by mixing 15 percent

chromium oxide w ith wheat flo u r and baking in to a hard bread which was

dried and ground through a medium mesh screen in a w iley m ill and then

mixed w ith each in d iv id u a l cows ra tio n in amounts th a t would give d a ily

in tak es o f approxim ately 15 grams o f chromium oxide per cow.

The feed in g schedule for the d if fe r e n t stages o f orchard grass hay

i s given in Table 10*

57

Table 10.

Feeding Schedule of "the Orchard Grass Hay Cut a t Various Stages

©f Maturity

Dates ( in c lu s iv e )

1-24-50 to 2-2-50

2-3-50 to 2-13-50

2-14-50 to 2-22-50

2-23-50 t© 3-4-50

3-5-50 to 3-14-50

3-16-50 to 3-25-50

3-26-60 to 4 -4-50

4-5-50 to 4-14-50

During each 10 day experim ental period d a ily a liq u o ts o f fe c e s sam­

p le s -were c o lle c te d in du p lica te as fo llo w s; ( 1 ) dried to constant weight

in a c ir c u la t in g a ir sample d r ier for d a ily determ inations o f dry m atter

eontent and ooznposited fo r the 10 day period for chemical a n a ly s is . ( 2 )

frozen d a ily and composited for the lo day period fo r determ ination o f the

p la n t pigment concen tration , and (3 ) composited in concentrated su lfu r ic

acid fo r n itrogen determ inations. Two samples o f the hay fed d a ily were

c o lle c te d in d u p lica te as ( 1 ) a 200 gram sample dried to constant w eight

fo r determ ination o f th e dry matter content and conxposited fo r the 10 day

period fo r chemical a n a ly s is , and ( 2 ) a d a ily sample composited as fed for

determ ination o f the p la n t pigment concentration .

Two samples o f a d a ily a liq u o te o f the urine were c o lle c te d in du­

p lic a te and stored w hile composited as fo llo w s; ( 1 ) frozen d a ily for

benzoic acid determ inations and ( 2 ) a c id if ie d d a ily w ith d ilu te (20 per­

cen t) su lfu r ic acid for n itrogen determ inations. D aily determ inations

Period

Prelim inary Period

Experimental Period

Prelim inary Period

Experimental Period

Prelim inary Period

Experimental Period

Prelim inary Period

Experimental Period

M aterial Fed

Stage 4 Orchard Grass« B tt It

Stage 3 Orchard GrassM II tt B

Stage 2 Orchard Grassft « n it

Stage 1 n n

tt » it it

58

o f the s p e c if ic grav ity o f "the urine and ■total ■volume o f the urine excreted

were made* A liquote amounts o f m ilk from each m ilking were preserved w ith

formaldehyde and were composited fo r each 10 day period fo r b u tter fa t

n itrogen determ inations*

In a d d ition to th e d a ily a liq u o te s of the f e c e s , "grab" samples were

taken from two passages d a ily o f each cow on three su ccessive days during

each ten day experim ental period* The "grab” samples were taken from two

forenoon and two afternoon passages o f fe c e s a t approximately the time o f

day th a t had been shown to g ive represen tative concentrations o f chromium

and l ig n in in the fe c e s o f previous t r ia l s (1 0 4 ). Duplicate samples were

dried fo r m oisture determ inations and chemical a n a ly s is and d u p licate

samples were frozen as voided for determ ination o f the p lan t pigment con­

cen tra tio n w ith the excep tion o f th e stage 4 orchard grass hay. Each

d u p lica te d a ily grab sample was handled and analyzed as an in d iv id u a l

sample designated as " f ir s t day p a r t ia l , second day p a r t ia l and th ird day

p a rtia l" fo r each stage o f orchard grass hay fed . Corrections were made

fo r the dry matter conten t o f the "grab" sample to th e t o t a l f e c a l dry

m atter excreted during the ten day c o lle c t io n period*

The d ates o f c o l le c t io n o f the "grab" samples are given in Table

11 .

59

Table 11

C o llec tio n Dates o f the "Grab" Samples taken o f each Stage

__________ ___________ o f Orchard Grass Hay

Orchard Grass Dates o f Fecal ^ r a b ” Samples

1 s t day 2nd day 3rd day

Stage 1 Apr* 10 Apr* 11 Apr* 12

Stage 2 Mar. 21 Mar* 22 Mar. 23

Stage 3 Feb* 28 Mar. 1 Mar. 2

Stage 4 Feb* 8 Feb. 9 Feb* 10

ANALYTICAL METHODS

Proximate Analyses

Proximate analyses o f the feed s and fe c e s -were made according to the

procedures described by the A ssociation o f O ff ic ia l A gricu ltu ral Chemists

(7 ) fo r crude p r o te in , ether e x tra c t, crude f ib e r , ash and n itro g en -free

extract*

L igain

Lignin was determined by the method of E l l i s , Mhtrone and Maynard

(6 2 ) .

P lan t Pigments

The e x tra c tio n of p lan t pigments in the feed and fe c e s were made by

the method o f Reid e t al* (158) but a u n it was a r b itr a r ily defined as th a t

amount o f p lan t pigment per m i l l i l i t e r o f 85 percent acetone ex tra c t th a t

gave a d en sity o f 1*0 w ith a Beckmann model DU spectrophotometer when read

in a 1 centim eter c e ll* Absorption curves o f the e x tr a c ts from the fe c e s

and orchard grass hays were very s im ilar to those reported by Reid e t a l

(158) fo r mixed hay and corresponding feces*

60

Chromium

The method used for the determ ination o f chromium oxide was a m odifi­

c a tio n o f the method of Edin e t e l . (6 1 ). S u ff ic ie n t sample to contain 20

to 40 • o f chromium oxide was weighed in to n ic k e l cru c ib les and ashed

u n t i l fr e e o f carbon* The c ru c ib les had a volume o f 125 m i l l i l i t e r s , a

heigh t o f 6 cen tim eters, suad a diameter o f 6 centim eters* The ashed ma­

t e r i a l was fused w ith a f lu x c o n s is t in g o f 4 grams o f potassium hydroxide,

2*7 grams o f sodium hydroxide, and 5*8 grams o f a mixture o f 158 grams

(1 mol) o f potassium carbonate, 106 grams (1 mol) o f anhydrous sodium car­

bonate, 202 grams (2 mol) o f potassium n it r a te , and 170 grams (2 mol) o f

sodium n itr a te* The totaL 12*5 grams o f the fu s io n mixture was weighed

out and added to each cru cib le w ith precautions to l im it the water uptake

o f the fu s io n mixture* The cru c ib les were then heated on a hot p la te u n t i l

the mixture became liq u id and sw irled a t 5 minute in te r v a ls during an addi­

t io n a l heatin g period o f 20 minutes* 1/Hhile the m aterial was s t i l l hot a

n ic k e l w ire , 1 m illim eter th ick and 15 centim eters long and formed in to a

sp ir a l a t one end, was placed in the fused m a ter ia l. A fter the mass had

s o l id i f i e d , the cru cib le was quickly heated w ith a g lass flame to m elt the

m ateria l around the w a lls so i t could be l i f t e d ou t w ith the n ic k e l w ire .

The m elted m ateria l was p laced in a 600 m i l l i l i t e r g la ss beaker, the

cru cib le was thoroughly washed w ith warm d i s t i l l e d w ater, and the washings

tran sferred to the beaker* The m aterial was then d isso lv ed in 150 to 200

m i l l i l i t e r s o f water. One m i l l i l i t e r o f 30 percent hydrogen peroxide was

added to the so lu tio n for reduction o f any 6 v a len t manganese to the 4

v a len t s ta te . Mien the so lu tio n had b o iled for one m inute, i t was f i l t e r e d

through a s in tered g la ss f i l t e r fun nel in to a 500 m i l l i l i t e r fla t-b o tto m

f la s k in order to remove the p rec ip ita ted manganese dioxide* Then 8*3

61

m i l l i l i t e r o f concentrated su lfu r ic acid and 2 .5 m i l l i l i t e r o f hydrogen

peroxide (30 percent) were added, and the so lu tio n heated to and kept a t

b o ilin g temperature fo r 5 minutes in order to destroy n i t r i t e s p resen t.

When th e so lu tio n had coo led , 2 m i l l i l i t e r s o f hydrogen peroxide (30 per­

cen t) and 34.5 m i l l i l i t e r s o f 6 .75 normal sodium hydroxide -were added and

the mixture heated again and b o iled for 5 minutes to ox id ize the reduced

chromium s a l t s to the chromate* Without in terru p tin g the b o il in g , 5

m i l l i l i t e r s o f 5 percent n ic k e l n itr a te •were added, and th e b o ilin g was

continued fo r 5 minutes longer to destroy the excess hydrogen peroxide.

A fter c o o lin g , the so lu tio n was a c id if ie d slow ly w ith 18 .3 m i l l i l i t e r s

e f concentrated su lfu r ic a c id , which had been b o iled prev iou sly for 4

hours. When th e so lu tio n had coo led , 10 m i l l i l i t e r s of the 10 percent

potassium iod id e so lu tio n were added and the so lu tio n t it r a te d with 0 .05

normal sodium th io su lfa te using a 1 percent starch so lu tio n as the in ­

d ic a to r .

EXPERIMENTAL RESULTS AND DISCUSSION

The average d a ily dry m atter consumption o f each animal r ec e iv in g the

four sta g es o f orchard grass hay and the fe c a l dry m atter excreted are g iw n

in Table 12. The dry matter consumed in th e grain fed each in d iv id u a l cow

i s the same for each d ig e stio n t r i a l while the dry matter consumption o f

the variou s stages o f orchard grass hay v a r ie s s l ig h t ly fbr the same ani­

mal due to s l ig h t v a r ia tio n s in the dry matter content o f the four stages

o f orchard grass hay fed . The chemical com position o f the grain and the

four sta g es o f orchard grass hay fed and the corresponding fe c e s for each

animal used in the d ig e st io n t r i a l s i s presented in Table 13. Each

62

a n a ly s is i s th e average o f a t le a s t four determ inations secured by making

r e p lic a te an a lyses on A and B samples o f eaoh m aterial* The range in the

stage o f m aturity represented by the four stages o f orchard grass hay i s

in d ica ted by the decrease in p ro tein content from 24*78 percent to 12*38

percent and th e increase in the crude f ib e r content from 26.88 percent to

35*05 percent w ith in creasin g m aturity.

The apparent d ig e s t io n c o e f f ic ie n t s o f the co n stitu en ts o f the to t a l

r a tio n ca lcu la ted from the consum ption-excretion r a tio s on samples from

t o t a l fe c a l c o l le c t io n are g iven in Table 14. I t i s evident th a t there was

l e s s change in the d ig e s t ib i l i t y o f the various co n stitu en ts between the

stage 1 and 2 orchard grass hays than occurred between the stages 2, 3 and

4 orchard grass hays* The apparent d ig e st io n c o e f f ic ie n ts o f the various

stages o f the orchard grass hay alone were ca lcu la ted by correcting the

f ig u r e s fo r th e t o t a l r a tio n using th e d ig estio n c o e f f ic ie n t s for corn

reported fo r c a t t le by Schneider (161) and are given in Table 15. A ll o f

the c o n stitu e n ts o f the proximate a n a ly s is have a considerably higher d i­

g e stio n c o e f f ic ie n t in the orchard grass hay cut in early m aturity than

in the hay cu t in la te maturity*

D igestion c o e f f ic ie n t s were a lso ca lcu la ted fo r the t o t a l c o lle c t io n

samples u s in g the r a tio technique w ith crude l i ^ i i n , corrected lig n in

(crude l ig n in - N itrogen x 6*25), chromium oxide and p lant pigm ents. Di­

g e stio n c o e f f ic ie n t s for the in e r t m ateria ls rati© techniques were c a l­

cu lated from the fo llow in g formula:

D igestion % Inert m ateria l in Feed % N utrient in F eces.« 100 - 100 X — ------------------------------- X-------------------------------- -

C o e ffic ie n t % Inert M aterial in Feces % N utrient in Feed.

The concentrations o f th ese co n stitu en ts in the feeds and fec es used for

c a lc u la t in g the d ig e stio n c o e f f ic ie n t s on the to ta l c o lle c t io n samples

65

arc given i s Table 16# The com position o f the fe c e s c o lle c te d as ”p a r t ia l

c o l le c t io n samples” on three days o f the ten day to ta l c o lle c t io n period

and used fo r c a lc u la tio n o f the d ig e stio n c o e f f ic ie n t s by the r a tio tech ­

niques on the p a r t ia l c o l le c t io n samples are given in Table 17# Lignin

a n a ly s is o f the p a r t ia l c o lle c t io n samples were not made since incom plete

reco v er ies o f l ig n in were secured w ith the t o ta l c o lle c t io n samples, thus

g iv in g somewhat lower d ig e s t io n c o e f f ic ie n t s when ca lcu la ted by the l ig n in

r a tio technique than when ca lcu la ted by the conventional t o t a l consumption-

e x cr e tio n r a tio s o f the various con stitu en ts*

The d ig e stio n c o e f f ic ie n t s of th e various co n stitu en ts for each in ­

d iv id u a l cow when ca lcu la ted by th e ra tio technique on the t o t a l c o lle c t io n

samples are given in Table 18 and the d ig e stio n c o e f f ic ie n ts for each cow

on each o f the three p a r t ia l c o lle c t io n days ca lcu la ted by the r a tio tech­

nique w ith chromium oxide are compiled in Table 19 and when ca lcu la ted by

the p la n t pigment r a t io technique are given in Table 20. A summary o f

th ese various techniques o f c a lc u la tin g the d ig e stio n c o e f f ic ie n t s i s given

in Table 21, u sin g th e average d ig e stio n c o e f f ic ie n ts o f the three cows

used w ith each stage o f orchard grass hay. The d ig e stio n c o e f f ic ie n ts

ca lcu la ted by the chromium r a tio and pigment r a tio techniques on both the

t o t a l c o l le c t io n samples and the three day p a r t ia l c o lle c t io n samples com­

pare very c lo s e ly w ith the standard to t a l c o lle c t io n technique for a l l o f

the c o n stitu e n ts o f the proximate analysis* D igestion c o e f f ic ie n t s c a l­

cu la ted by the l ig n in r a tio technique using the crude l ig n in conten ts o f

the ra tio n and fe c e s gave s l ig h t ly lower d ig e stio n c o e f f ic ie n t s than were

obtained by the to ta l f e c a l c o lle c t io n technique* The d ig e st io n c o e f f i ­

c ie n ts ca lcu la ted by the true l ig n in rati© technique are s l ig h t ly lower

than those c a lc til ated by th e orude l ig n in r a tio technique.

A rev iew o f the l ite r a tu r e on various d ig e s t io n t r i a l techniques

in d ic a te s th a t previous comparisons o f d ig e s t io n t r i a l techniques have

64

not included a comparison o f severa l methods o f determining d ig e s t io n co­

e f f i c i e n t s in the same d ig e st io n t r i a l . The present study has made a com­

parison o f seven d if fe r e n t methods o f ca lcu la tin g d ig estio n c o e f f ic ie n t s

w ith each o f four d if fe r e n t stages o f orchard grass hay fed w ith a uniform

amount o f gra in .

A nalysis o f variance by the method o f Snedecor (169) shows a s i g n i f i ­

cant d iffe re n c e between th ese seven methods of ca lcu la tin g d ig e stio n co­

e f f ic ie n t s * There i s a c lo se check, however, between th e d ig e stio n co­

e f f i c i e n t s ca lcu la ted by the standard to t a l f e c a l c o l le c t io n , the chromium

r a t io , and the p la n t pigment r a tio techniques* The r e s u lt s showed th a t

the fe c a l recover ies o f lign in . are somewhat l e s s than 100 percent which

gave lower d ig e s t io n c o e f f ic ie n t s ca lcu la ted "by the l ig n in r a tio technique

than th ose obtained by the to ta l f e c a l c o lle c t io n technique. Further

stu d ies would be necessary to a scerta in i f the d ig e s t ib i l i t y o f l ig n in

in orchard grass hay i s due to d iffe r e n c e s in the nature o f the l ig n in

is o la te d from the feed and fe c e s studied; whether the metabolism o f l ig n in

in orchard grass hay i s d if fe r e n t than l ig n in metabolism in some other

p la n ts ; or i f l ig n in metabolism o f second growth orchard grass hay might

be d if fe r e n t t l» n th a t o f a f i r s t growth o f the p la n t. S a tis fa c to ry re­

s u lts w ith the l ig n in r a tio method o f ca lcu la tin g d ig e stio n c o e f f ic ie n t s

have been reported fo r other ra tio n s (62 , 69, 71, 103, 178)*

The dry m atter d i g e s t i b i l i t i e s o f the ra tion s contain ing Stage 1 and

Stage 2 hays were sim ilar (Table 21). The s l ig h t ly h igher dry m atter d i­

g e s t ib i l i t y o f the Stage 2 hay compared w ith the Stage 1 hay was accompanied

by a decrease in the l ig n in con ten t. The Stage 2 hay was presumably cut

during the period o f th e most rapid rate o f growth o f the grass. Huffman

( 9 3 ) has pointed out th a t the decreased d ig e s t ib i l i t y o f the dry m atter

65

o f p la n ts i s b e lieved to be a ssoc ia ted w ith l ig n i f ic a t io n o f the c e l l w a ll

although the t o t a l amount o f l ig n in does not appear to be the determ ining

fa c to r .

The apparent d ig e s t ib i l i t y o f th e crude p ro te in and crude f ib e r was

higher in the ra tio n contain ing Stage 1 orchard grass than in the ra tio n

conta in ing Stage 2 orchard grass but th e d i g e s t i b i l i t i e s o f the n itrogen -

fre e e x tr a c ts were s im ila r . D ig e s t ib i l i t y o f the dry m atter, p ro te in ,

crude f ib e r , and n itrogen—fr e e e x tr a c t fra c tio n s decreased p ro g ress iv e ly

in the Stage 2 , Stage 5 and Stage 4 orchard grass hays.

SUMMARY

A comparison o f seven d if fe r e n t methods o f determining d ig e s t ib i l i t y

c o e f f ic ie n t s was made w ith each of four d ig e st io n t r i a l s u sin g three m ilk-

in g cows fed orchard grass hay cut a t four stages o f m aturity and a simple

grain m ixture. The conventional ten day t o t a l f e c a l c o lle c t io n method was

used as a standard for comparison w ith the r e su lts of the other techn iqu es.

Chromium oxide was added to the grain ra tio n as an exogenous in e r t sub­

stan ce . Lignin and c e r ta in p lan t pigments were determined as in e r t ma­

t e r i a l s normally present in the r a tio n . The concentrations o f these three

in e r t m ater ia ls in the r a tio n fed and in the fe c a l samples taken from an

a liq u o te o f the to t a l c o lle c t io n were used in ca lc u la tin g the d ig e stio n

c o e f f ic ie n t s by the in e r t m ateria l r a tio technique. A dditional "grab"

samples taken on three days o f the ten day c o lle c t io n period were analyzed

and the d ig e s t io n c o e f f ic ie n t s ca lcu la ted on each o f these days by the

chromium r a tio and p lant pigment r a tio techn iques. Incomplete recover ies

o f l ig n in w ith each o f the t o t a l c o lle c t io n t r ia l s made i t im practical to

c a lc u la te th e d ig e s t io n c o e f f ic ie n t s by th e l ig n in r a tio technique w ith

the "grab" samples.

66

Comparable d ig e s t io n c o e f f ic ie n t s were secured w ith the standard ben

day consum ption-excretion method and th e chromium and p lan t pigment r a tio

techniques when ca lcu la ted w ith both th e to ta l c o lle c t io n samples aid the

averages o f th ree days p a r t ia l c o l le c t io n or "grab” samples.

D igestion c o e f f ic ie n t s ca lcu la ted by the crude l ig n in and the corrected

l ig n in r a tio techniques u sin g the to ta l f e c a l c o lle c t io n samples were both

s ig n if ic a n t ly lower than th e d ig e st io n c o e f f ic ie n ts ca lcu la ted by the stan­

dard censum ption-excretion method in th ese t r i a l s .

The change in chemical com position of the orchard grass hay w ith in ­

creasin g m aturity resu lted in a decrease in p ro te in content o f from 24.78

t© 12.58 percent and an in crease in crude fib er content o f from 26.88 to

35.05 percen t.

D ig e s t ib i l i t y o f the various co n stitu en ts in the four stages o f

orchard grass hay o f in creasin g m aturity was; dry matter 69.0 , 7 0 .4 ,

65.9 and 59 .4 percent; p r o te in , 6 5 .7 , 6 0 .7 , 55.4 and 54.3 percent; crude

f ib e r , 8 2 .5 , 7 8 .6 , 72 .0 and 69.1 percent; and n itro g en -free e x tr a c t ,

6 9 .3 , 7 4 .7 , 6 8 .0 , and 57.3 percent r e sp e c tiv e ly .

67

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2. Andersen, A* C*, and L* Frederiksen*V erdauliohkeitsversuche an Milohkuhen* Biedermanns Zentralbl*T* Agri cu ltu r chemie u* r a t i one l ie n L andw irtschaftsbetr., 5 : 3 3 4 , 1935.

3* Andersen, A* C. , and J* E* Winther,F o rd /je lig h ed sfo rs /g med M alkek/er, i l l Gm Be stemmelse a f Ford^Qelighed ved Edins saakaldte nLedkropps M etode.” Ber, F ore/gslab . (Copenhagen), 155:117-186, 1934*

4* Armitage, B* R ., R. Ashworth and W. S* Ferguson.Determ ination o f l ig n in in p lant m ateria ls o f high p rote in con­te n t . J* Soe. Chem. In d ., (London), 67:241-243, 1948.

5. Armsby, H. P*The n u tr it io n o f Farm Animals. The Macmillan Co. New York. 1917.

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7 . A ssoc ia tion o f O f f ic ia l A gricu ltural Chemists.O f f ic ia l Methods o f A nalysis o f the A ssociation o f O ff io ia l Agr icupEura 1 cHeinTsts^ Washington, 4 , D. C, 7tTT""Ed. 1950.

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Baker, F . , and S . T. H arriss.M icrobial d ig e stio n in the rumen (and caecum) w ith sp ec ia l r e fer ­ence to the decomposition of stru ctu ra l c e l lu lo s e . N u trition A bstracts & R evs., 17:3-12 , 1947.

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Burroughs, W*, and P. Gerlaugh.The in flu en ce o f soybean o i l meal upon roughage d ig e st io n in c a t t l e . J. Animal S c i . , 8 :3 -8 , 1949.

Burroughs, W., P. Gerlaugh and R. M. Bethke.The in flu en ce o f a l f a l f a hay and fra c tio n s o f a l f a lf a hay upon th e d ig e st io n o f ground corncobs. J. A nim al S c i . , 9: 207-213, 1950.

Burroughs, W., P. G erlau^i, B. H. Edgingtom and R. M. Bethke.Further observations on the e f f e c t o f p rote in upon roughage d ig e s t io n in c a tt le * J . Animal S c i . , 8*9-18, 1949.

70

9 5 .

36.

37*

38*

39*

40*

41*

42.

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75. F ran cois, A ., A* M. Leroy and Genevieve Levy.The fa te o f methexy groups during d ig e stio n o f p ec tin and l ig n in by ruminants. Coxopt. ren d ., 232$132S-1325, 1951.

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T A B L E S

85

Table 12.Average D aily Dry Matter Consumed and Excreted by Cows Fed

Four Stages o f Orchard Grass Hay.

: bry Matter Consumed i Drys s Matter

Hay Fed Animal _* . Hay Grain Total s ExcretedgQLS. gms. gnis. gras.

Stage 1 X65 s 10,052 1,981 12,033 8 3,4332408 8 10,454 3,557 14,011 s 3,782N635 8 6,433 2,786 9,219 s 2,326

Stage 2 X65 8 10,315 1,981 12,296 3 3,4712408 8 10,727 3,557 14,284 3 3,668H635 8 6,601 2,786 9,387 s 2,318

Stage 5 X65 8 10,241 1,981 12,222 s 4,1172408 1 10,651 3,557 14,208 s 4,348N635 8 6,554 2,786 9,340 8 2,649

Stage 4 X54 8 7,290 2,496 9,786 s 3,3162408 : 10,530 3,557 14,087 8 4,9553J635 8 6,480 2,786 9,266 i 3 ,102

86

T ab le 13*

Composition o f the Dry Matter o f Feeds and Feces used in D igestionT ria ls o f Orohard Grass Hay*

M aterial P rotein Fiber IT* F* E*—w ~

EtherExtract Ash

- j r

Grain 86 9*18

Orchard Grass

Stage 1 24. 78

Stage 2 15*80

Stage 3 13*00

Stage 4 12*38

Feoes

Stage 1X65 24*86

2408 26.45N635 26.97

Stage 2X65 20*19

2408 20.73N635 19.38

Stage 3X65 15.96

2408 16 .84N635 15*46

Stage 4X54 12.64

2408 14 .34N635 14.50

2.17

26.88

28.15

31.77

35.05

15.6014.2614.69

20.2518.9218.44

24.4722.6922.93

24.7623.76 24.22

81.14

35.02

45.82

44. 24

41.16

35.7237.4535.79

38.1841.4241.74

39.2741.1141.74

41.8843.88 43.84

3.63

3.99

3.46

3.91

4 .24

8.097.277.67

7.656.827.19

7 .847.187.53

7 .437.067.09

3.88

9 . 53

6.77

7.08

7.17

15.7314.8014.88

13.7312.4713.25

12.46 12.18 12. 34

11.1410.9611.55

87

T ab le 14*

Apparent D ig estio n C o effic ien ts o f the Ration Constituents by Cows Fed. Four Stages o f Orchard Grass Hay

DryMatter P rotein Fiber N.F.E.

EtherExtraci

Stage 171.5 68.1 80 .5 76.1 4 1 .2

2408 73.0 66.0 81.3 78.4 49.8H635 74.8 66.1 80.9 81.6 50.0

Average 73.1 66.7 80.9 78.7 47.0

Stage 2X65 71.8 61.3 76 .2 79.1 38.0

2408 74 .3 63.1 77.7 80 .4 51.1H635 75.3 65.4 77.7 81.8 48.4

Average 73.8 63.3 77.2 80 .4 45.8

Stage 3.......X5F 66.3 56.5 69.5 73.7 31.6

2408 69.4 57.0 71.5 76.5 43.0H635 71.6 63.0 71.7 78.6 44.1

Average 69 .1 58.8 70.9 76.3 39.6

Stage 4.......XB* 66.1 59.8 67.5 72.1 35.7

2408 64.8 56.2 68.8 69.9 39 .4N635 66.5 60.6 67.6 72.4 41.4

Average 65.8 58.9 68 .0 71.5 38.8

88

T able 15

Apparent D igestion C o effic ien ts o f the C onstituents o f Orchard Grass Hay* out a t Pour Stages o f M aturity

DryMatter P rote in Fiber N.F.E.

EtherExtract

Stage 1X65

2408H635

68*668*669.9

67*664*864*6

81*583*083.0

69.368.4 70.3

33.138.2 55*6

Average 69.0 65.7 82.5 69*3 35.6

Stage 2 X65

2408 H635

69.171 .470.8

59*859*163.1

77.079.1 79.6

75.074.474.7

28.237.232.7

Average 70.4 60.7 78.6 74.7 32.7

Stage 5 X65

2408 N635

62.5 63.865.5

54.052.859.3

70.1 72.773.2

67.567.6 68.9

21.729.127.2

Average 63.9 55.4 72.0 6 8 .0 26.0

Stage 4X54

2408H635

59.357.658 .2

55.651.555.9

68.569.869.0

59.355.956.6

20 .125.524.7

Average 58 .4 54.3 69.1 57.3 23.4

♦D igestion c o e f f ic ie n t s o f Orchard Grass Hay ca lcu la ted ”^y d iffe r e n c e ” u sin g the d ig e st io n c o e f f ic ie n t s o f co m reported by Schneider (1947).

89

T ab le 16

Composition o f th e Dry Matter o f Feeds and Feces used for C alcu lating D igestion C o e ff ic ie n ts by the Ratio Technique on T otal C o llec tio n Samples

Lignin Content

M aterial* Crude 1 Lignin

Corrected : Lignin s

ChromiumOxide

PlantPigment

Grain 86 X65

2408 N.635

X54

Orchard Grass Stage 1 Stage 2 Stage 3 Stage 4

%

.518

.518

.518

.623

7.776.747.979.56

%

.505

.505

.505

.607

5.715.12 6.328 .1 2

.7341 • 4318 .5620 .5200

units/gnu

5.415.415.41 7 .63

901.3595.3 562.1 484.0

FecesStage 1

X65 2408 N655

21.6120 .2020.63

14.7713.6913.74

.4367 • 4246 .6667

2634.0 2203.3 2414.2

Stage 2 X65

2408 $635

19.0416.9917.63

13.2312.1112.71

.4320

.4362

.6315

1779.0 1742.51897.1

Stage 5 X65

2408 $635

19.3217.3618.12

14.5213.1813.36

.3352

.3356

.5262

1268.91274.71395.0

Stage 4 X54

2408 $ 6 5 5

18.8317.8818 .64

15.0914.7215.25

.3974

.3157

.4852

963.5994.7997.0

90

T able 17*

C o m p o sitio n © f th e P ry M a tter o f F e c e s u sed fo r C a lc u la t io n o f D ig e s t io nC o e f f i c i e n t s b y th e R a tio T echnique on P a r t i a l C o l l e c t io n Sam ples

Stageand

Animal Day P rote in Fiber H.F.E.Ether

ExtractChromium

OxideP lant

Pigment% % % % % u n its /m .

Stage 1X65 1 22.65 15.31 40.24 7.73 .4634 2370.6

2 23.78 14.41 39.05 8 .02 .4353 2494.63 24.31 15.60 37. 64 8 .06 • 4459 2433.1

2408 1 22.91 14.48 42.30 6.74 • 4541 2049.92 22.60 14.23 44.29 6.54 .4231 1983.33 22.84 13.77 43.31 7.28 • 4299 2192.1

N635 1 24.31 13.64 41.66 6.71 .6672 2167.62 25.54 12.52 41.52 6.86 .6340 2147.63 23# 84 13.02 39.85 8.29 • 6692 2239.0

Stage 2X65 1 17.24 20.66 41.78 7.63 • 4555 2080.5

2 17.65 20.22 41.77 7.55 • 4586 2005.83 17.87 20.35 41.71 7.69 • 4289 2058.6

2408 1 20.34 18.92 41.52 6.75 .4527 1881.22 17.56 19.02 45.34 7.08 .4716 1816.43 17.57 18.74 45.40 7.00 .4713 1788.6

N635 1 19.46 17.35 42.43 7.75 .6979 2127.12 18.35 18.12 44.27 7.16 .6820 1939.53 17.45 18.15 44.43 7.55 .6875 1884.5

Stage 3X65 1 14.80 25.70 39.91 7.90 .3560 1460.0

2 14.98 24.36 40.81 8.11 .3735 1486.23 14.91 23.32 41.54 8.31 .3768 1532.2

2408 1 16.08 22.70 40.43 8.54 .3803 1405.72 15.13 23.91 41.15 8.08 .3470 1363.33 14.56 23.18 42.79 7.77 .3511 1379.5

N635 1 16.02 21.49 43.13 7.65 .5745 1292.22 13.71 24.00 42.94 7.92 .5749 1388.43 15.70 21.25 43.71 7 .92 .5878 1450.7

Stage 4X54 1 12.46 24.21 44.26 7.00 •4193 - -

2 12.31 24.40 44.72 7.16 .4400 —

3 12.74 23.59 44.40 7.33 .4264 —2408 1 12.85 24. 29 46.57 6.87 .3271 —

2 13.00 23.99 46.10 6.91 .3320 —

3 13.66 24. 24 44.54 7.41 .3259 —H6o5 1 13.23 23.70 45.44 7.14 .5000 —

2 12.42 24. 21 45.64 7.30 .4714 - -

3 13.46 23.64 44.65 7.23 • 4883 —

91

T ab le 18*

D ig e s t io n C o e f f i c i e n t s C a lc u la te d b y th e R a tio T echn ique on th eT o ta l C o l l e c t io n Sam ples

Method AnimalDry Ether

P rotein Fiber

Chromium Stage 1

Stage 2

Stage

Stage

Pigments Stage

Stage 2

Stage 3

St«ge 4

CrudeLignln

1 X65 72*3 73.6 81.1 74.4 43 .02408 74 .2 67 .4 82.1 79.3 51.3R635 74 .6 65.8 80.7 81 .4 49 .6

2 X65 72.6 62.5 76.9 79.7 39.82408 76 .6 66.6 80.0 82.0 55.7N635 74.8 64.9 77.6 81 .2 47 .2

3 X65 64.5 54.3 67.8 72.2 27.92408 67.9 54.9 70.1 75.4 40 .2N635 68.2 58.5 68.2 76.0 37.3

4 X54 66.6 64.3 68.9 71.1 36.62408 65.7 57.3 69.6 70.7 41 .0N635 65.3 59.2 66.6 71.4 39.3

1 X65 71 .4 72.7 80.4 73.5 41 .12408 69.7 61.8 79.1 75.8 43.0R635 73.9 64.9 80.2 80.9 48.2

2 X65 71.9 61.5 76 .2 79.1 38 .22408 74.3 63.2 78.0 80 .2 51.2N635 77.8 69.2 80.4 83.5 53,6

3 X65 62.8 52.1 66.3 71.9 24.52408 66.8 53.4 69.1 74 .6 38.2N635 71.6 63.0 71.6 78.6 44.0

4 X54 62.5 59.9 65.0 67.5 28.72408 63.5 54.5 67.6 68.8 37.1H635 65.2 59.0 66.5 71 .3 39.1

1 X65 69.6 72.0 79.2 71.9 37 .42408 70.6 63.0 79.7. 76.5 44 .7N635 73.0 63.6 79.5 80.2 46 .4

2 X65 69.9 58.7 74.5 77.6 33.72408 70.1 57.0 74.0 77.2 43.3N635 72.8 61.5 75.5 80.1 43.1

3 X65 65.0 54.9 68.3 72.6 28.92408 65.3 51.2 67.7 73 .4 35.2N635 68.7 59.2 68.8 76.4 38 .4

4 X54 60.7 58.0 63.3 65.9 25.22408 58.8 48 .6 65.4 64.8 29.0N635 63 .4 57.0 64.8 69.9 36.0

92

T a b le 18* C ontinued

DryMethod Hay Jftnimal Matter

Corrected Id gain

Stage 1 X652408N635

67*268.069.9

Stage 2 X652408N635

67.768.071 .2

Stage 3 X652408N635

63.663.7 66.2

Stage 4 X542408N635

58.958.663.1

P rote in Fiber E .F .E .Ether

E xtract

68.7 77.6 69.6 32.459.6 77.8 74.3 39.759.6 77.2 78.0 40 .0

55.8 72.7 76.1 29.054.0 72.2 75.6 39.359.2 74.0 78.8 39.7

53.2 67.0 71.5 26.049.0 66.2 72.2 32.355.9 66.3 74.5 33.5

56.1 61.7 64.4 21.948 .4 63.2 64.6 28.356.5 64.4 69.5 35.3

93

T able 1 9 .

D ig e s t io n C o e f f i c i e n t s C a lc u la te d by t h e Chromium R a tioT ech n iq u e on t h e P a r t ia l C o l le c t io n Sam ples

C ollec tion Dry Hay______ Animal Day_______ Matter

Stage 1 X65 1 73*92 72.23 72.9

2408 1 75.82 74.13 74.5

N635 1 74 .62 73 .33 74.7

Stage 2 X65 1 74.02 73.03 72.4

2408 1 76.32 77.23 77.2

N635 1 76.12 75.53 75.7

Stage 3 X65 1 66 .62 6 8 .13 68.4

2408 1 71 .62 68.93 69.2

N635 1 70.82 70.93 71.5

Stage 4 X54 1 68 .42 69.93 68.9

2408 1 66.72 67 .23 66.6

N635 1 66.12 64.13 65.3

P rotein Fiber N.F.E.Ether

Extract

73 .4 82 .5 75.3 48.770.3 82.5 74.5 43.370.3 81.5 76.0 44 .473 .4 73.0 78.1 57.871.8 8 2 .1 75 .4 56.172.0 83.0 76.4 51.969.2 80.8 81 .4 49.666.0 82.8 77.3 53.660.9 83.0 79.6 47.0

69.6 77.6 78.9 43.167.7 77.2 78.1 41.566.6 76.6 77.6 39.172.3 79.4 79.9 51.871.6 80.0 81.1 54.171.7 80.3 81.1 54.766.4 79.7 82.0 47.067.6 78.3 80.8 49.969.4 78.4 80.8 47.7

60.1 68.2 73.4 31.661.5 71.2 74.1 33.162.0 72.7 73.9 32.062.0 73.5 78.5 37.060.8 69.5 76.0 34.662.7 70.7 75.7 37.960.7 72.7 77.2 41.561.5 69.5 77.4 39.662.4 73.6 77.5 40.9

66.7 71.2 72.5 43 .468.6 72.3 73.5 44.866.5 72.4 72.8 41.762.9 69.8 69.9 44 .263.0 70.6 70.6 44 .760.4 69.9 71.0 39.660.9 68.1 71.1 40.361.0 65.4 69.2 35.259.2 67.4 70.9 38.1

94

T able 20

D ig e s t io n C o e f f i c i e n t s C a lc u la te d by th e P igm ent R a tio T echniqueo n t h e P a r t i a l C o l l e c t io n Sam ples

S*X_Stage 1

Stage 2

AnimalC o llection

DayDry

Matter P rotein Fiber N. F.E.Ether

E xtract

X65 1 68.2 67.6 78.7 69.9 37.52 69*8 67.7 80.9 72.3 38 .33 69*0 66.1 78.8 72.6 36.5

2408 1 67.1 63.8 76.9 70.3 42 .62 66.0 63.1 76.6 67.8 4 2 .43 69.3 66.2 77.5 71.5 42 .0

N635 1 70.9 64.8 78.0 78.8 42.32 70.6 62.7 81.1 75.1 49 .13 71.8 66.6 81.1 77 .4 41 .2

X65 1 76.0 71.9 79.3 80 .5 47 .32 75.1 70.1 79.0 79.8 45 .93 75.7 70.5 79.4 80 .3 4 6 .4

2408 1 76.2 72.2 79.3 79.8 51.62 75.3 69.3 78.4 79.5 50.33 74.9 68.9 78.3 79.2 50.2

N635 1 80 .2 72.3 83.2 85.1 56.32 78.3 71.3 80.8 83.0 55.73 77.7 71.9 80.2 82.4 52.0

X65 1 67.7 61.4 69.2 74.3 33.92 68.3 61.6 71.3 74.2 33.33 69.2 63.0 73 .4 74.5 33.7

2408 1 69.9 59.8 72.0 77.3 33.72 69.0 61.0 69 .6 76.2 34.93 69.4 62.9 70.9 75.5 38.2

N635 1 69.4 58.7 71 .3 76.1 38.62 71.5 67.1 70.2 78.0 40.93 72.7 63.6 74.7 78 .4 43.5

Stage 4^*^

(1 ) S u itab le samples to re not av a ila b le for determ ination o f the p lan t pi©nent concentration o f the feces for a l l animals used in the t r i a l w ith Stage 4 Orchard Grass hay*

95

T ab le 21

Comparison o f D igestion C o effic ien ts Calculated by several methods on Four Stages o f Orchard Grass Hay p lu s Grain

3 3C on stitu en t: Standard:

Chromium: Ratio :

t ig n in katio Crude : Corrected

: P i gment: Chromium t Ratio : Ratio

:Pigment i Ratio

Stage 1Dry Matter 73 74 71 68 72 74 69P rote in 67 69 66 63 67 70 65Fiber 81 81 80 78 80 81 79N* F.E, 79 78 76 74 77 77 73Ether Ext* 47 48 43 38 44 50 41

Stage 2 Dry Matter 74 75 71 69 75 75 77P rotein 63 65 59 56 65 69 71Fiber 77 78 75 73 78 79 80N.F*E. 80 81 78 77 81 80 81Ether Ext* 46 48 40 36 48 48 51

Stage 3Dry Matter 69 67 66 65 67 70 70P rotein 59 56 55 53 56 62 62Fiber 71 69 68 67 69 71 71N*F.E. 76 75 74 73 75 76 76Ether Ext* 40 35 34 31 36 36 37

Stage 4tr y Matter 66 66 61 60 64 67 - -P rote in 59 60 55 54 58 63 —Fiber 68 68 64 63 66 70 —U*F*E* 72 71 67 66 69 71 —

Ether Ext* 39 39 30 29 35 41 ——

PART I I

STUDIES ON THE COMPOSITION OF LIGNIN ISOLATED FROM ORCHARD

GRASS HAY CUT AT FOUR STAGES OF MATURITY AND FROM THE CORRES­

PONDING FECES

INTRODUCTION

Lignin has been reported to be in d ig e s t ib le by a number o f workers

(7 , 9 , 13, 14 , 16 , 17, 19, 38 ). Other reports in d ica te th a t varying amounts

o f l ig n in may be d igested or broken down in the ruminant d ig e s t iv e tr a c t

(4 , 8 , 10, 11, 18, 21, 22, 27).

Since the chemical structure o f l ig n in has not been esta b lish ed i t i s

not fe a s ib le to i s o la t e or determine a product o f uniform composition from

d if fe r e n t m a ter ia ls . Certain c h a r a c te r is t ic s o f crude l ig n in preparations

vary considerably depending upon the m ateria l from which i t i s iso la te d and

the method used for i t s is o la t io n . Extensive stu d ies have been made o f -the

c h a r a c te r is t ic s o f lig n in is o la te d from various woods but only lim ited

stu d ie s have been reported on l ig n in prepared from forage p lan ts important

in animal feed in g .

P h il l ip s e t a l . (33) found 4 .34 percent n itrogen in the l ig n in ob­

ta in ed from oat p la n ts 7 days old which decreased to 1.26 percent n itrogen

in the l ig n in from p lan ts 84 days o ld . Bondi and Meyer (4) reported from

1 .18 to 1 .63 percent n itrogen in the l ig n in from four grass sp ec ies and

from 2.92 to 3 .36 percent n itrogen in the l ig n in from four legumes. The

l ig n in is o la te d from the corresponding fe c e s a l l had s l ig h t ly higher n itr o ­

gen con ten ts. They a lso showed th a t the l ig n in n itrogen was r e s is ta n t to

h y d ro ly s is by strong acid (5 N su lfu r ic acid ) and weak acid (0 .5 N hydro­

c h lo r ic acid ) and by pepsin added to the weak a c id . These r e s u lt s led them

to conclude th a t the n itrogen in crude l ig n in preparations was not present

as p ro te in n itrogen . Furthermore, the d ig e s t iv e enzymes o f the ruminant

did not reduce th e n itrogen content o f the l ig n in .

98

Norman and Jenkins (25) believed th a t p rotein degradation products

fo llo w in g th e treatm ent o f p lan t m aterial vdth strong acid r esu lted in high

l ig n in y ie ld s rather than p rote in per se* paloheimo (2 6 ) , Wfcksman and

Stevens (4 0 ) , P h i l l ip s (2 8 ) , and DeMan and DeHeus (12) have corrected crude

l ig n in va lu es by deducting the nitrogen content m u ltip lied by the factor

6*25* P h il l ip s (29) la te r f e l t th a t because there was not a constant re­

la t io n between the amount o f protein added to samples fo r the determ ination

o f l ig n in and th e s iz e o f the error involved th a t the apparent l ig n in values

should not be corrected but the percent o f nitrogen in the l ig n in should be

reported*

Thomas and Armstrong (39) found amino acids in the hydro ly sa te s from

crude l ig n in and proposed th a t the fa c to r 6*25 for converting l ig n in n itr o ­

gen to p ro te in was valid* DeMan and DeHeus (12) found the tyrosin e and the

tryptophane n itrogen in the l ig n in iso la te d from Lolium perenne was in

agreement w ith th a t fo r the true p rote in of the grass* The tryptophane

n itrogen was determined on l ig n in iso la te d without the use o f concentrated

su lfu r ic acid*

Bondi and Meyer (4 ) found about 5 percent methoxyl in the l ig n in ob­

ta in ed from legumes and about 10 percent methoxyl in the l ig n in iso la te d

from various g r a sse s . They a lso found very l i t t l e d ifferen ce in the methoxyl

content o f the l ig n in iso la te d from the corresponding fe c e s which would in ­

d ic a te th a t there i s very l i t t l e breakdown o f the ether linkages in the

l ig n in m olecule during passage through the d ig e stiv e tract* O xidation o f

the l ig n in from various p la n ts gave y ie ld s o f from 4*2 to 21.6 percent

aldehydes w hile ox id ation o f the fe c a l l i gains gave n e g lig ib le q u a n tities

©f aldehydes, in d ic a tin g a change in the side chains attached to the l ig n in

m olecule during passage through the in te s t in a l t r a c t . The l ig n in from the

99

grasses gave a much higher percentage o f aldehydes fo llow in g ox id a tion than

the legumes but th e r a tio o f v a n i l l in to p-hydroxy-benzaldehyde was approx­

im ately 2 to 1 in a l l ca ses .

Stone, B lundell and Tenner (37) found th a t the r a tio s o f v a n i l l in to

syringe aldehyde d id n ot remain constant in the wheat p lan t a t d if fe r e n t

sta g es o f growth sin ce the percentage o f syringealdehyde was lower than

v a n i l l in in the young p lan ts and higher in the more mature p la n ts . Con­

current in creases in the methoxyl content o f the l ig n in were observed.

Csonka, P h i l l ip s and Jones (10) and P h ill ip s e t a l . (34) reported a

lo s s o f 36.7 percent o f the methoxyl groups associa ted w ith the l ig n in in

a r a tio n o f hay, grain and s i la g e fed to a cow. Francois, Leroy and Levy

(15) reported th a t 50 percent o f the methoxyl content o f the l ig n in d is ­

appeared in the d ig e s t iv e tr a c t of ruminants fed a l f a l f a hay alone and in

combination w ith wheat, and dried beet pulp* The apparent d ig e s t ib i l i t y

o f the l ig n in o f a l f a l f a was approximately 8 percent.

Pazur and DeLong (27) P h ill ip s e t a l . (34) and Csonka, P h ill ip s and

Jones (10) have reported increased urinary excretion o f hippuric acid when

increased amounts of l ig n in are fed and f e l t th at t h i s ind icated a metab­

o lism o f l ig n in in the animal body. Rogozinski and Starzewska (36) f e l t

th a t l ig n in was in d ig e s t ib le by sheep and played no part in the formation

o f h ippuric a c id .

This study was conducted to determine certa in c h a r a c te r is t ic s o f the

l ig n in is o la te d from orchard grass hay cut a t four stages o f m aturity and

from the corresponding fe c e s o f dairy cows fed th ese forages.

EXPERIMENTAL PROCEDURE

The method o f conducting the d ig estio n t r ia l s and the c o lle c t io n and

handling o f the samples have been prev iou sly presented (part l ) .

100

The n itrogen content o f the l ig n in was determined "by the microk^eldahl

method o f the A ssoc ia tion o f O f f ic ia l A gricu ltural Chemists (3) on samples

o f the l ig n in iso la te d from the various m ateria ls by the method o f E l l i s ,

Matrone and Maynard (13)*

The t o t a l methoxyl groups in the feed s fed and the feces voided and

a lso the methoxyl content o f the l ig n in iso la te d from th ese m ateria ls were

determined by the method o f Clark (5 , 6 ) .

The benzoic a c id concentration in the urine was determined by the

method o f Kingsbury and Swanson (20)*

RESULTS AND DISCUSSION

The amounts o f l ig n in consumed and excreted and the percent recovery

o f l ig n in in the fec es and the percent o f l ig n in d igested are given in

Table 22. Since l ig n in recover ies were a l l somewhat lower than i s d esirab le

fo r a m ateria l to be su ita b le for use as an in e r t tracer m aterial i t ex­

p la in s the tendency for the lower d ig e stio n c o e f f ic ie n ts prev iou sly pre­

sented (Part I ) th a t were ca lcu la ted by the l ig n in r a tio technique. "When

planning t h is experiment i t was p ostu lated th at i f the lig n in o f orchard

grass was p a r t ia l ly d igested th at there might be a range in the d ig e s t ib i l ­

i t y o f l ig n in th a t would show higher d ig e s t i b i l i t i e s o f the l ig n in in im­

mature orchard grass than in th© more mature s ta g e s . Since lower d ig e s t­

i b i l i t y o f the l ig n in in the immature orchard grass hay ra tion was secured

i t seemed d esira b le to in v e stig a te some o f the c h a r a c te r is t ic s o f the l ig n in

iso la te d from the feeds and fe c e s from th ese d ig estio n t r i a l s . The n itrogen

content o f the l ig n in is o la te d from the four stages o f orchard grass hay

and the corresponding fe c e s are presented in Table 23. The l ig n in iso la te d

from the immature orchard grass had a higher n itrogen content (4 .25 percent)

than th e l ig n in iso la te d from the most mature orchard grass (2 .4 1 p ercen t).

L ignin is o la te d from the corresponding fe c e s had average n itrogen contents

101

0 f 5*19 and 2*91 percent r e sp ec tiv e ly . The p ro te in content o f the dry

m atter o f th e immature grass was 24*78 percent w hile the p ro te in content

o f the most mature orchard grass was 12*38 percent* The p ro te in content

o f th e corresponding fe c e s averaged 26.09 and 13.83 percent r e sp e c t iv e ly .

Small d iffe r e n c e s were obtained between the n itrogen content o f the l ig n in

from each stage o f orchard grass hay and the n itrogen content o f the l ig n in

is o la te d from th e corresponding feces* The ”true l ig n in 11 contents o f each

stage o f hay and the corresponding fe c e s were ca lcu la ted by correctin g the

crude l ig n in content for the n itrogen content o f the l ig n in m u ltip lied by

the fa cto r 6*25* While there i s considerable controversy concerning the

nature of the n itrogen p resen t in the l ig n in preparations, th e work o f

DeMan and DeHeus (12) and Thomas and Armstrong (39) in d ica tes th a t the

use o f a p ro te in fa c to r may be ju s t i f ie d in converting the n itrogen pres­

ent in the l ig n in to protein*

The crude l ig n in contents o f the four stages o f orchard grass hay o f

in creasin g m aturity were 7*77, 6*74, 7*97, and 9*56 percent resp ectively*

Lignin i s gen era lly considered as a con stitu en t that in creases w ith ad­

vancing m aturity o f the p lan t (2 , 9 , 23, 30, 31, 32, 33, 35, 41)* Other

work (2 , 24) w ith orchard grass has shown th a t the l ig n in content i n i t i a l l y

decreases and then p ro g ress iv e ly in creases w ith advancing m aturity and

th ese changes are concommitant w ith progressive increases in the crude

f ib e r content and p rogressive decreases in the crude p rotein content*

These r e s u lt s are in agreement w ith those found in th is in vestiga tion *

There i s evidence th a t sim ilar changes occur in timothy (3 1 ) , oa ts (3 3 ) ,

perennial ryegrass ( 2 ) , t a l l fescu e (2 ) and burnet ( 2 ) . This pattern of

change has n o t been observed in a l f a l f a , t r e f o i l and yarrow ( 2 ) . m other

th ese changes are a p h y sio lo g ica l c h a r a c ter is t ic o f the growth o f cer ta in

102

grasses or whether there i s an inherent error in the determ ination o f l ig n in

in immature grasses has not been determined.

The tru e l ig n in in tak es and excretion fo r each stage o f hay fed was

ca lcu la ted and th ese data w ith the recoveries and d ig e s t i b i l i t i e s o f the

tru e l ig n in are presented in Table 24# The apparent d ig e stio n c o e f f ic ie n ts

fo r true l ig n in are higher than those ca lcu la ted for crude lign in* I f the

reco v er ies o f the true l ig n in were higher than those found fo r the crude

l ig n in one could assume th a t a higher d ig e s t ib i l i t y o f the n itrogen contain­

in g fr a c t io n o f the crude lig n in had resu lted in greater lo s s e s o f t h i s por­

t io n in passing through the d ig e stiv e tract* Comparison o f the n itrogen

contents o f the l ig a in iso la te d from the various orchard grass hays and

the corresponding fe e e s (Table 23) does not in d ica te th at th is occurred*

Since other stu d ies (1 0 ,2 7 ,3 4 ) have ind icated th a t degradation pro­

ducts o f l ig n in may cause increased urinary excretion of benzoic ac id ,

determ inations were made of the benzoic acid excretion by each animal fed

the four stages o f orchard grass hay* Table 25 g ives the amounts o f crude

l ig n in and true l ig n in fed and d igested by each animal and the urinary

ex cretio n o f benzoic aoid per 100 grams of l ig n in fed and d ig ested . The

benzoic ac id ex cretio n per u n it of lig n in fed is somewhat lower in the

mature hay than in the other three stages o f le s s mature hays* I f the

amount o f urinary benzoic acid excretion i s influenced la r g e ly by the

degree o f l i^ i i n degradation th ese fig u res would in d ica te a lower d i­

g e s t ib i l i t y o f l ig n in in the more mature orchard grass hay. This i s not

supported by the consum ption-excretion fig u r es fbr crude l ig a in given in

Table 22. I t i s p o ss ib le th a t other co n stitu en ts o f immature orchard

grass contribute to the formation and excretion o f benzoic ac id .

The methoxyl contents o f the feed and fe c e s on a dry weight b a s is

are g iven in Table 26. A p rogressive increase in the t o t a l methoxyl

103

content o f th e hay occurs w ith in creasin g m aturity from 1,41 percent to

1.85 percent and sim ilar in creases occur in the methoxyl content o f the

fe c e s from animals fed these hays. The methoxyl content of the l ig n in from

the immature hay i s lower (7*84 percent) than th a t from the other three

stages which are sim ilar in methoxyl content (1 0 .6 0 , 10.73 and 10.41 per­

c e n t) . Comparable changes occur in the methoxyl content o f the l ig n in

is o la te d from the corresponding fe c e s . Bondi and Meyer (4) found approx­

im ately 10 percent methoxyl groups in the l ig n in iso la te d from severa l

sp ec ies o f grass. Their work a lso in d ica tes th at each stru ctu ra l u n it o f

the l ig n in m olecule from grasses contains two methoxyl groups which would

give a th e o r e t ic a l methoxyl content o f 9 .9 percent. P h il l ip s e t a l . (33)

found the methoxyl content of the lig n in o f oa ts increased from around

4 to approxim ately 15 percent during growth to 84 days o f age. Sim ilar

changes occurred in the l ig n in o f barley p lan ts (32) and timathy p lan ts

(31) during development. The percentages o f the to ta l methoxyl groups

th a t were a ssoc ia ted w ith the l ig n in in the four stages of orchard grass

hay in crea sin g in m aturity were 3 1 .9 , 3 5 .1 , 40 .7 and 45 .4 percent, re­

s p e c t iv e ly . Adams and Castagne ( l ) found 8 2 .4 percent and 81.7 percent

o f the to t a l methoxyl groups o f wheat and o a t straw, r e sp e c t iv e ly , in the

l ig n in fr a c t io n . P h i l l ip s ani Goss (28) found from 52.0 to 81.1 percent

o f the t o t a l methoxyl groups a ssocia ted with the l ig a in fra c tio n o f barley

p la n ts a t various sta g es o f development. From 39.3 to 85 .7 percent o f the

t o t a l methoxyl content o f the oat p lant was found in the iso la te d l ig n in

by P h i l l ip s e t a l . (2 9 ) .

There i s not much change, however, in the percentage of the t o t a l

methoxyl groups which are a sso c ia ted w ith tl^ lig n in iso la te d from the

fe c e s o f cows fed orchard grass hay cut a t four stages o f m aturity. This

would suggest th a t there i s a higher d ig e s t ib i l i t y o f the n on -lign in

104

methoxyl in the immature forage and th is i s evident in a comparison o f the

d ig e s t io n c o e f f ic ie n t s o f the various fra c tio n s o f the methoxyl groups th a t

are a lso given in Table 26* D ig e s t ib i l i t y o f the to ta l m ethojyl content

o f th e ra tio n and the methoxyl groups not associated w ith the l ig n in both

decrease w ith in creasin g m aturity o f the p lant while there i s p r a c t ic a lly

no change in the d ig e s t ib i l i t y o f the methoxyl groups associa ted with the

l ig n in ,

SUMMARY

The apparent d ig estio n c o e f f ic ie n ts o f l ig n in in ra tion s containing

orchard grass hay cu t a t four stages o f m aturity ranged from 3 ,8 to 16,0

p ercen t.

The l ig a in s iso la te d from four stages o f orchard grass o f in creasin g

m aturity had n itrogen contents o f 4 ,2 5 , 4 ,1 5 , 3,53 and 2,41 percent. The

average n itrogen contents o f the l ig a in s iso la te d from the corresponding

fe c e s were 5 ,1 9 , 4 ,1 3 , 3 ,62 and 2,91 percent. Apparently no degradation

o f the n itrogen associa ted w ith the l ig n in in orchard grass hay occurred

during d ig e s t io n by dairy cows. There may be errors in the determ ination

o f l ig n in th a t are unaccounted fo r in the a n a ly s is o f m ateria ls d iffe r in g

w idely in other c o n stitu e n ts .

The apparent d ig e stio n c o e f f ic ie n ts for the l ig n in corrected for n itr o ­

gen content was somewhat higher (7 ,5 to 19.8 percent) than the d ig e stio n

c o e f f ic ie n t s fo r crude l ig n in .

The benzoic acid ex cretio n in the urine per 100 grams o f l ig n in fed

was lower when feed ing the most mature hay than when feed ing the other

three le s s mature hays. There was no r e la t io n between the d ig e stio n co­

e f f i c i e n t o f l ig n in and the urinary excretion o f benzoic ac id .

The to ta l methoxyl content o f the hay fed was lower than the to ta l

methoxyl content o f corresponding fe c e s on a dry matter b a s is . The methoxyl

105

con ten ts o f the l ig n in iso la te d from the various hays was higher than the

methoxyl contents o f the l ig n in iso la ted from the corresponding fe c e s .

The percent o f the t o t a l methoxyl content in the hay th a t was associa ted

w ith the l ig n in increased w ith increasing m aturity of the orchard g ra ss.

Higher proportions o f the to ta l methoxyl content o f the fe c e s was associa ted

w ith the l ig n in in the fe c e s and on ly s l ig h t changes in th is percentage

©ocurred when hays of a wide range o f maturity were fed .

D ig e s t ib i l i t y o f the to ta l methoxyl content and the n on -lign in methoxyl

content o f the ra tion decreased w ith increasing maturity o f the orchard

grass hay. D igestion o f the l ig n in methoxyl groups ranged from 20.3 to

31.6 percent and showed no co n sisten t trend in r e la t io n to the stage o f

m aturity o f the hay fed .

106

literature cited

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2 . Armstrong, D. G ., H. Cook and B. Thomas.The l ig p in and c e llu lo se contents o f cer ta in grassland sp ec ies a t d if fe r e n t stages o f growth. J. Agr. S c i . , 40:93-99 , 1950.

3. A sso c ia tio n o f O f f ic ia l A gricu ltural Chemists.O f f ic ia l methods o f A nalysis o f the A ssociation o f O ff ic ia l XgrTcuIH;ura3^^Eeml^t^"'Washin'^onM? ,,' I)*.' C. "TEE E3T. T*T£f.—

4. Bondi, A* H*, and H. Meyer.Lignins in young p lan ts . Biochem. J . , 43:248-256, 1948*

5. Clark, E. P.XLI. Microchemical methods. J. Assoc. O ff. Agr. Chemists. 22:100, 1939.

6. Clark, E. P.Report on microohemical methods. Alkoxyl determ ination.J . Assoc. O ff. Agr. Chemists. 22:622-624, 1939.

7. Corbin, J . E.Unpublished t h e s i s , Univ. o f Kentucky, 1947. Cited by Forbes,R. M., and W. P. Garrigus. J. Animal S c i . , 7:373-382, 1948.

8 . Cramp to n , E. W.Pasture s tu d ie s . XIV. The n u tr it iv e value o f pasture herbage. Some problems in i t s estim ation and some r e su lts thus fa r ob­ta in ed at MacDonald C ollege. S c i. A gr., 19:345-357, 1939*

9. Cramp to n , E. W., and L. A. Maynard*The r e la t io n o f c e llu lo s e and lig n in to the n u tr it iv e value o f animal fee d s . J . N u trition 15:383-395, 1938.

10. Csonka, F. A ., M. P h il l ip s and D. B. Jones.S tu d ies on l ig n in metabolism. J. B io l. Chem., 85:65-75 , 1929.

11. D avis, R. E ., C. 0 . M iller and I . L. Lindahl.Apparent d ig e s t ib i l i t y by sheep o f l ig n in in (dehydrated) pea and lima bean v in e s . J* Agr. Research, 74:285-288, 1947.

12. DeMan, T. J . , and J. G. DeHeus.L ignin in grass (w ith sp ec ia l reference to the n itrogen presentin the l ig n in p reparation ). Rec. Trav. Chem., 69:270-276, 1950.

13. E l l i s , G. H ., G. Matron© and L. A. Maynard.A 72-percent su lfu r ic acid method fo r the determ ination o f l ig n in and i t s use in animal stu d ies . J . Animal S c i . , 5:285-297, 1946.

107

14. Forbes, E. B ., R. p# E l l io t , R. W. S w ift, W. H. James and VivianF. Smith.V aria tion in determ inations o f d ig e s t iv e capacity o f sheep.J . Animal S c i . , 5*298-305, 1946.

15. F ran cois, A ., A. M. Leroy and Genevieve Levy.Le sort des radicaux methoxy au cours de la d ig estio n des p ec tin es e t lig n in e s par le s Bovins. Comp. ren d ., 232*1325- 1325, 1951. ^

16. Gray, F. V.The d ig e stio n of c e llu lo s e by sheep. The ex ten t o f c e llu lo s e d ig e stio n a t successive le v e ls o f the alim entary tr a c t . J. Expt. B io l* , 24*15-19, 1947.

17. H ale, E. B ., C* $T* Duncan and C. F. Huffman.Rumen d ig e st io n in the bovine w ith some observations on the d ig e s t ib i l i t y o f a l f a lf a hay. J . Dairy S c i . , 23:953-967, 1940.

18. Juon, P.Uber den E in flu ss der Futterkonservierung auf d ie Be stand te i le der Zellwand. Landw. V ers. S ta ., 120*129-224, 1934.

19. Kane, E. A ., W. C. Jacobson and L. A. Moore.A comparison o f techniques used in d ig e s t ib i l i t y stu d ies w ith dairy c a t t le . J. N u tr itio n , 41*583-596, 1950.

20. Kingsbury, F. B. and W. W. Swanson.A rapid method for determ ination o f hippuric acid in u r in e .J. B io l. Chem. 48*13-20, 1921.

21. Louw, J. G.The r e la t iv e d ig e s t ib i l i t y of the con stitu en ts o f the carbo­hydrate complex o f grasses at su ccessive stages o f growth w ith reference to th e ir p a r tit io n in to crude f ib e r and n itrogen -free e x tr a c t according to the standard method for fee d in g stu ff a n a ly s is . Onderstepoort J. V et. S c i. 17*165-179, 1941.

22. McAnally, R. A.D igestion o f straw by th e ruminant. Biochem. J . , 36*392-399, 1942.

23. Norman, A. G.The a sso c ia tio n o f xylan w ith c e llu lo se in cer ta in stru ctu ra l c e l lu lo s e s . Biochem. J . , 30*2054-2072, 1936.

24. Norman, A. G.The com position o f forage crops. I I I . Cocksfoot. Changes m the herbage during growth, with and without ad d ition s o f n itr o ­genous f e r t i l i z e r . Biochem. J. 33*1201-1208, 1939.

25. No m an, A. G ., and S. H. Jenkins.The determ ination o f l ig n in . I I . Errors introduced by the presence o f p ro te in s . Biochem. J . , 28*2160- 2168, 1934.

108

26*

27.

28.

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SO.

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3 3 .

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37.

Paloheimo, L.Beitrage zur Ligninbeslsiinnrung mit Saurehydrolyse. Biochem. Z ., 214:161-174, 1929.

Pazur, J . H ., and W. A. DeLong.Pasture s tu d ie s . XXVTII. E ffec t of l ig n in content and o f stage o f maturi-ty o f dry clover forage on the urinary excretion o f aromatic ac id s by sheep. S c i . A gr., 28:39-46, 1948.

P h i l l ip s , M.The quant i t a t i ve determ ination o f m ethoxyl, l ig n in and c e llu lo s e in plant m a ter ia ls . J . Assoc. O ffic . Agr. Chemists. 15:118-131, 1952.

P h i l l ip s , M.Studies ©n the qu an tita tive estim ation o f l ig n in . I I . E ffe c t ©f cer ta in p rotein s on the determination o f l ig n in by the fuming HC1 method. J. Assoc. O ff ic . Agr. Chemists. 22*422-427, 1939.

P h i l l ip s , M., J . Davidson and H. D. Weihe.S tudies o f l ig n in in wheat straw with reference to lodging.J . Agr. S c i . , 43:619-626, 1931.

P h i l l ip s , M., B. L. Davis and H. D. Welhe.Composition o f the tops and roots o f the timothy p lan t a tsu ccessive stages o f growth. J. Agr. Research. 64:533-546, 1942.

P h i l l ip s , M., and M. J. Goss.Composition of the leaves end sta lk s o f barley a t su ccessive stages o f growth, with sp ec ia l reference to the formation o f l ig n in . J . Agr. Research, 51:301-319, 1955.

P h i l l ip s , M., M. J. Goss, B. L. Davis and H. Stevens.Composition o f the various parts o f the oat p lan t a t su ccessivesta g es o f growth, w ith sp ec ia l reference to the formation o f l ig n in . J . Agr. Research. 59:319-366, 1939.

P h i l l ip s , M., H. Weihe, D. B. Jones and F. A. C so n k a .The dem ethoxylation o f l ig n in in the animal body. Proc. See. B io l. Med., 26:320-321, 1929.

R it te r , G. J .Chemistry o f Wood. VTI. R elation between methoxyl and lig n in in wood. Ind. Eng. Chem., 15:1264-1266, 1923.

R ogozinski, F ., and M. Starzewska.Tiber d ie Verdauung des Lignins bei den Wiederkauem. B u ll.Acad, polon . S c i . B, 1243-1252, 1928.

Stone, J . E ., M. J. B lundell and K. G. Tanner.The fonaation o f l ig n in in wheat p la n ts . Can. J. Chem. 29: 734-745, 1951.

109

38. S w ift, R. W. , E. J . Thacker, A* Black, J* ^ B ratzler and W. H. James#D ig e s t ib i l i t y o f rations for ruminants as a ffec ted by proportion ©f n u tr ie n ts . J . Animal S c i# , 6:432-444, 1947.

39. Thomas, B#, and D. G. Armstrong.A study o f some methods at present used for the determ ination o f l ig n in . J . Agr. S c i . , 59:335-346, 1949.

40. Waksroan, S . A ., and Stevens, E# R#A system o f proximate chemical analysis o f p lant m ater ia ls .Ind# Eng. Chem. Anal. Ed. 2:167-173, 1930.

41. WDodman, H. E ., and J . Stewart.The mechanism of c e llu lo se d ig e stio n in th e ruminant organism.I I I . The aotion o f c e llu lo se s p lit t in g b acteria on the fib re o f c er ta in ty p ic a l fee ding s tu f f s . J . Agr. S c i . , 22:527-547,1932#

T A B L E S

110

T ab le 2 2 .

Crude Lignin Fed and Excreted by Each An imal Receiving Various Stages of

Orchard Grass Hay plus Grain#

Average 'Average D aily Crude D aily

Lignin Consumed Lignin Lignin LigninHay Fed Animal Ifay Grain Total Excreted Recovery Digested

gms. gms. gms. gms. % %

Stage 1 X65 781*0 10.3 791.3 741.8 93.7 6 .32408 812.3 18.4 830.7 763.9 92.0 8 .0N635 499*8 14*4 514.2 479.7 93.3 6 .7

Stage 2 X65 695*6 10.3 705.9 660.8 93.6 6 .42408 723*4 18 .4 741.8 623.2 84.0 16.0N635 445*2 14.4 459.6 408.7 88.9 11.1

Stage 3 X65 816.3 10.3 826. 6 795.4 96.2 3.82408 848*9 18.4 867.3 754.8 87.0 13.0N635 532.4 14*4 536.8 480.0 89.4 10.6

Stage 4 X54 696*9 15.5 712.4 624.5 87.7 12 .32408 1006.6 18.4 1025.0 886.0 86 .4 13.6N635 619*4 14.4 633.8 578.2 91 .2 8 .8

I l l

T ab le 23 .

nitrogen Content o f Crude Li gain Iso la ted from Various Stages of Orchard Grass Hay and the

Corresponding Feces

Stage o f M aturity M aterial Animal

CrudeLignin Hitro gen

True*Lignin

% % %

Stage 1 Hay ------- 7.77 4.25 5.71

Feces X65 21.61 5.07 14.772408 20.20 5.16 13.69N635 20.63 5.34 13.74

Stage 2 Hay ------- 6.74 4 .15 5.00

Feces X65 19.04 4.35 13.232408 16.99 4.07 12.11N635 17.63 3.98 12.71

Stage 3 Hay ------- 7.97 3.53 6.21

Feces X65 19.32 3.49 14.922408 17.36 3. 69 13.18U635 18.12 3.67 13.36

Stage 4 Hay ------- 9.66 2.41 8 .12

Feces X54 18.83 3.18 15.092408 17.88 2.69 14.72N635 18.64 2.85 15.25

\ f Crude Lignin minus (U x 6 .25 )

112

Table 24.

True Li gain Fed and Excreted by Each Animal R eced in g Various Stages of Orchard Grass Hay

plus Grain

Average D aily True D ailyLignin Consumed Li gain Lignin Lignin

Hay Fed Animal Say (jrain Total Excreted Recovery D igested©ns* gpos. gms. gms. % %

Stage 1 X65 573.4 10.0 583.4 507.0 86.9 13.12408 596.4 18.0 614.4 517.7 84.3 15.7H635 367.0 14.1 381.1 319.5 83.8 16.2

Stage 2 X65 515.3 10.0 525.3 459.2 87.4 12.62408 535.9 18.0 553.9 444.2 80.2 19.8N635 329.8 14.1 343.9 294.7 85.7 14. 3

Stage 3 X65 636.3 10.0 646.3 597.8 92.5 7 .52408 661.7 18.0 679.7 573.1 84.3 15.7H635 407.2 14.1 421.3 353.9 84.0 16.0

Stage 4 X54 592.0 15.2 607.2 500.4 82 .4 17.62408 855.1 18.0 873.1 729.4 83.5 16.5H635 526.2 14.1 540.3 474.1 87.8 12 .2

115

T able 25*

Urinary E xcretion of Benzoic Acid by Animals Fed Orchard Grass Hay Cut a t Four Stages o f M aturity

Average Aver a g e ______ Benzoic Acid E xcretion_______Stage D aily D aily Gns/100 gms. Gms./lOO gms.

and Crude L ignin True Lignin Total Crude Lignin True Li gain Animal Fed D igested Fed D igested D aily ffed. Digested Fed toigestecT

©as. gms. gms. ©ms. ©as.

Stage 1 X65

2408 H655

791831514

49.5 66.834.5

583614381

76.496.761.6

139115

80

17.6 13.815.6

280.8172.2231.9

23.818.721.0

181.9118.9129.9

Stage 2 X65

2408 N635

706742460

45 .1118.6

50.9

525554344

66.1109.7

49.2

136156115

19.321.025.0

301.6151.5225.9

25.928.233.4

205.7 142.2233.7

Stage 3 X65

2408 N635

827867537

31.2112.5

56.8

646680421

48.5106.6

67.4

122118

97

14.813.618.1

391.0104.9170.8

18.917 .423.0

251.5110.7143.9

Stage 4X54 712

2408 1025 N635 654

87.9139.0

55.6

607873540

106.8 143.7

66. 2

1049261

14.69 .09 .6

118.366.2

109.7

17.110.511.3

97.464.092.1

114

T ab le 26 .

Methoxyl Content o f the Feed and Feces Dry Matter and "the Lignin Iso la te d from th ese M aterials, and D igestion C oeffic ien ts for

Various Fractions of Methoxyl Groups

Lignin D igestion C o effic ien ts Stage Methoxyl lion-

and Total Lignin in Total Lignin LigninM aterial Animal Methoxyl Methoxyl Total Methoxyl Methoxyl Methoxy

i % %

Stage 1 Hay 1.41 7,84 31.9

Feces X652408N635

1.841*771 .72

7.757.397.70

63.659.363.4

58.459.761.0

16.023.521.5

77.375.4 79.2

AV* 1.78 7.61 62.1 59.7 20.3 77.3

Stage 2 Hay 1.51 10.60 35.1

Feces X652408H635

2.092.082.08

8.808.788.88

58 .453.4 56.7

56.457.857.9

28.435.131.3

70.869.171.3

At . 2.08 8.82 56.2 57.4 31.6 70.4

Stage 3 Hay 1.62 10.73 40.7

Feces X652408N635

2.252.082.40

9.308.689.52

62.257.255.4

47.552.747.4

20.733.027.2

65.265.3 59.9

At * 2.24 9.17 58.3 49.2 27.0 63.5

Stage 4 Hay 1.85 10.41 45.4

Feces 2408H635

2.352.50

9.779 .96

60.959.6

45.542.4

22.817.7

62.860.6

Av* 2.43 9.87 60.3 44.0 20.3 61.7

FART III

A STUDY OF THE CRUDE FIBER AND NITROGEN-FREE EXTRACT FRACTIONS

OF ORCHARD GRASS HAY AND THE DIGESTIBILITY OF SOME OF

THE CONSTITUENTS BY MILKING COWS

INTRODUCTION

Certain lim ita tio n s o f the ■widely used system o f fo o d stu ffs a n a ly s is

inaugurated by Henneberg and Stohmann (22 ) have undoubtedly been recognized

s in ce the method was f i r s t proposed* The value and usefu ln ess o f th is

system o f a n a ly s is has a lso been recognized and demonstrated through many

years accumulation o f r e su lts on a wide v a r ie ty of feed m ater ia ls . The

ex ten sive com pilation o f feed composition and d ig e s t ib i l i t y data by

Morrison (36) and Schneider (44) are a tr ib u te to the past and present

u se fu ln ess o f the Henneberg system o f feed analysis* The stu d ies o f

A xelsson (3 , 4 , 5 , 6 , 7 ) , D ijk stra (1 2 ) , DuokwoHh (1 3 ) , H allsworth (2 0 ) ,

Homb (24 , 25), Jarl (26 , 27), Lancaster (2 9 ) , McMeekan (3 4 ), Nordfeldt

e t a l . (37) and O lofsson (40) a l l in d ica te d e f in ite value in determining

the crude fib er content of feed s since the high negative co rre la tio n be­

tween the crude f ib er content and the d ig e s t ib i l i t y and feed in g value o f

a feed c e r ta in ly j u s t i f y the continued use o f the crude f ib e r determina­

t io n in the absence o f a more desirable scheme o f analysis*

There are numerous reports in the lite r a tu r e d iscu ssin g the m erits

and lim ita t io n s o f p a r tit io n in g the carbohydrates of feed s in to crude

f ib e r and n itro g en -free ex tra c t fr a c t io n s . Several authors (8 , 9 , 10,

29, 31, 33, 35, 37, 38, 39, 49, 51) have c r it ic iz e d the Weende system

o f determining the content of crude f ib e r in a feed and c a lc u la tin g the

amount o f n itro g en -free e x tr a c t as being u n sa tisfa c to ry p r in c ip a lly be­

cause the co n stitu en ts th a t make up the crude f ib e r and n itrogen -free

e x tr a c t fr a c t io n s vary grea tly with d if fe r e n t p lan t sp ec ies and d iffe r e n t

m a ter ia ls and a lso with d if fe r e n t conditions of determining the crude

f ib e r fr a c t io n .

117

Crampton and Maynard (10) have compared the average d ig e stio n co­

e f f i c i e n t s o f the n itrogen -free ex tra ct and crude f ib e r fra c tio n s in

various c la s se s o f fe e d s . Dry roughages, pasture herbage and s ila g e had

39, 67, and 28 percent, r e sp e c tiv e ly , of the cases in which the crude f ib e r

was as high or higher in d ig e s t ib i l i t y than the n itrogen -free e x tr a c t .

This demonstrated the v a r ia b il i ty in the com position, d ig e s t ib i l i t y , and

feed in g value o f crude f ib e r from various sources.

Norman (38) pointed out th a t crude fib er determined by the conven­

t io n a l method was not a s in g le compound but con sisted o f c e llu lo se and

l ig n in w ith some hem icellu lose and p e c tin . Several m odifications o f the

We end e system o f an a ly sis fo r crude f ib e r have been proposed but they

a l l have the same c r it ic ism even though the rep ro d u ctib ility i s s a t is ­

fa c to r y . N ordfeld t e t a l . (37) compared severa l methods for the de­

term ination o f crude f ib e r and found them to give good rep ro d u etib ility

but d if fe r e n t methods gave d iffe r e n t values for crude f ib e r . They a lso

showed th a t the composition o f the crude fib er was d if fe r e n t in d iffe r e n t

feed s and the crude f ib er from a p articu lar feed was d iffe r e n t from th a t

o f the corresponding fe c e s . They also demonstrated a se le c t iv e d ig e st­

i b i l i t y o f the l ig n in , c e llu lo se and pentosan fra c tio n s which are the

main components o f the crude f ib e r . This work emphasized the value of

l ig n in , c e l lu lo s e and pentosan determ inations to supplement the crude

f ib e r determ ination and thus would give more u sefu l inform ation o f the

nature o f the carbohydrate fra c tio n in feeds and fe c e s .

Knowledge o f th ese lim ita tio n s associa ted with the determ ination

o f crude f ib e r has stim ulated in te r e s t in other systems o f fe e d s tu ffs

a n a ly s is th a t would not leave such a large portion of the feed a n a ly ti­

c a l ly undetermined. A few in v e stig a to rs have attempted to account for

118

n ea r ly a l l the dry matter of various feeds and feo es by a n a ly tica l d eter ­

m inations -which leave comparatively small amounts o f undetermined sub­stances*

Probably the e a r l ie s t stu d ies o f the summative an a ly sis o f common

feed in g s tu f f s in the United S ta tes were done by Headden (21) and Widtsoe

and Stewart (50)* Headden (21) p artition ed clover hay in to sugars,

d e x tr in s , starch , xy lan s, lign on es, c e l lu lo s e , m oisture, ash , p r o te in s ,

m ateria ls extracted by ether and m ateria ls extracted by a lcoh ol and water

corrected fo r sugar and dextrins* Hie had 4 .8 percent o f the t o t a l p lan t

m ateria l undetermined by th is system o f analysis* Widtsoe and Stewart

(50) p a r tit io n ed the dry matter o f a l fa lfa in to the e th er e x tr a c t , water

e x tr a c t , acid e x tr a c t , a lk a li e x tr a c t , f ib e r , and ash in the f ib e r fra c ­

tions* They made progressive ex traction s w ith each so lvent on the r e s i ­

due remaining a fte r previous extraction s thus accounting for a l l o f the

dry matter* This sytem would not be too u sefu l for d ig e s t ib i l i t y stu d ies

sin ce the m ateria l ex tracted by each solvent from the feed and fe c e s

would probably vary w idely .

Crampton and Whiting (11) proposed a scheme o f an a ly sis which de­

termined the percentage o f lig n in by d ifferen ce a fter making a n a ly tic a l

determ inations o f c e l lu lo s e and soluble carbohydrates* Ferguson (15)

analyzed wheat straw for i t s content o f ether ex tra ct, crude p ro te in ,

ash , l ig n in , true c e l lu lo s e , pentosans in c e llu lo s e and fur fur aldehyde,

m th th is system o f a n a ly s is he had 13.7 percent o f the dry matter un­

determined which he c a lle d "other carbohydrates”* Ferguson (16) a lso

analyzed severa l forage samples fo r the ind iv idu al stru ctu ra l co n stitu ­

e n ts o f the c e l l w all and a lso the non-structural co n stitu en ts and

seoured variab le q u a n titie s o f undetermined co n stitu e n ts . A nalysis o f

119

"w&vy young M-gh p ro te in gross gave undetermined fr a c tio n s ©mounting to on ly

4 .5 percent o f the dry matter while the mere mature forages had over 16

percent o f the dry m atter undetermined* Reid (42) reported that larger

amounts o f the dry matter o f mature grass than o f younger grasses was un­

determined by the sum o f the l ig n in , c e l lu lo s e , h em ice llu lo se , p e c tin ,

starch , t o t a l sugar, ash , crude p rotein and ether ex tract percentages*

Flanders (17) recen tly reported a summative an a ly sis o f timothy hay

by determining ash , benzene-aloehol e x tr a c t iv e s , water e x tr a c t iv e s , p e c tic

substances, h em ice llu lo ses , alpha c e l lu lo s e , l ig n in and proteins* A study

o f the four hem icellu lose fra c tio n s extracted ind icated th a t they were

m ixtures and th e ir composition varied from one plant source to another

(18)* The h em ice llu lose fra c tio n s showed comparable v a r ia tio n s in the

uronic ac id anhydride and pentose contents w ith in p lant fa m ilie s but not

between p la n ts o f d if fe r e n t fam ilies*

The presen t sta tu s of our knowledge o f the carbohydrate co n stitu en ts

o f forage has been w e ll desoribed by P ercival (41) in a recent d iscu ssio n

o f the su b ject. He sta ted th a t , "Although an immense amount o f routine

a n a ly t ic a l work has been carried out on forage crops in th e p a s t , we are

s t i l l ignorant, in the main, o f what i s measured tinder such headings as

crude f ib e r , t o ta l carbohydrates and so on*tt

I t seemed d esirab le to study cer ta in o f the chemical co n stitu en ts o f

the crude f ib e r and n itro g en -free extract fra c tio n s th a t could be d eter­

mined as e ith e r d e f in ite chemical substances or that would be representa­

t iv e o f sim ilar substances when determ inations are made on w idely d if fe r e n t

m a ter ia ls such as feeds and feces* While such a method o f a n a ly s is i s not

r e a d ily app licab le to routine determ inations i t would give u se fu l informa­

t io n on the r e la t iv e d i g e s t i b i l i t i e s o f various fra c tio n s o f the carbo­

hydrate complex o f forage p lan ts and a lso might permit lo g ic a l grouping

120

o f c er ta in o f th ese co n stitu en ts th a t would be b io lo g ic a l ly sim ilar and

a lso might be e a s i ly grouped for convenient chemical determinations#

The ob ject o f th is in v e stig a tio n was to determine the d ig e stio n co­

e f f i c i e n t s o f c er ta in con stitu en ts th a t are ord in ar ily grouped in the crude

f ib e r and n itro g en -free ex tract fra c tio n s and a lso to a scerta in what per­

centage o f the dry matter o f the feed and fec es would be accounted for by

a more d e ta ile d system o f analysis#

EXPERIMENTAL PROCEDURE#

The method o f conducting the d ig estio n t r ia l s and the c o lle c t io n and

handling o f the samples has been prev iou sly described (p art i)#

C ellu lo se was determined by the method o f Matrone, E l l i s and Maynard

(3 2 ).

Pentosans were determined as the fu rfu ra l y ie ld in g co n stitu en ts ac­

cording to the o f f i c i a l method o f the A ssociation of O ff ic ia l A gricu ltu ral

Chemists (1 ) and the weight o f fu rfu ra l phloroglucide ca lcu lated as the

pentosan eq u iva len t. The pentosan content o f the crude Matrons c e llu lo s e

was determined on a sample o f crude c e llu lo se which was divided in to

separate samples fo r determ inations o f the pentosan and c e llu lo se con­

te n ts .

Starch was determined on the grain samples by the o f f i c i a l d ia sta se

method w ith subsequent acid h yd ro lysis o f the A ssociation o f O ff ic ia l

A gricu ltu ra l Chemists ( 1 ) . Starch was determined on the hay and fe c e s

samples by the method o f Hbffpauir (2 3 ).

Determ inations o f the reducing sugars were made by ex tractin g the

m ateria l w ith 80 percent a lcoh ol according to the method o f Thomas, Melin

and Moore (4 8 ) , in version w ith hydrochloric a c id , and determining the

reduced copper a fte r b o ilin g the ex tra ct w ith copper su lfa te -a lk a lin e

121

ta r tr a te so lu tio n by the dichrom ate-ferric sulfate-diphenylam ine procedure

described by Ieonard e t a l . (3 0 ).

Organic ac id s were determined ly the method o f Somers (45)* Aqueous

e x tr a c tio n s o f the m aterial were made in a Waring blender a fter add ition

o f s u f f ic ie n t 3 normal hydrochloric acid to bring the pH to approximately

1*0* The a c id if ie d ex tracts were heated in a steam bath to remove carbon

d io x id e , made to a convenient volume a t 25 degrees centigrade and then a

50 m i l l i l i t e r a liq u o te ■was adjusted to pH 7*8 w ith sodium hydroxide (3 nor­

mal fo llow ed by 0*05 normal sodium hydroxide) and t itr a te d to pH 2 .6 with

0 .05 normal n i t r ic ac id . The organic acids were ca lcu la ted as the equiv­

a le n t amount o f m alic acid*

RESULTS AND DISCUSSION.

The com position o f the crude f ib er and n itre gen-free ex tra c t fra c ­

t io n s o f the feeds fed during the d ig estio n t r ia l s conducted on the orchard

grass hay cut a t four stages of m aturity are given in Table 27. The con­

ven tion a l proximate system o f a n a ly sis for feeds inclu des determ inations

o f the p r o te in , ash , ether e x tr a c t , and crude fib er percentages and c a l­

c u la tio n o f the n itro g en -free e x tr a c t fra c tio n o f the feed by d iffe re n c e .

With t h i s system , the percentages th a t were determined by d ifferen ce

(n itro g en -free e x tra c t) ranged from 35.0 to 45.8 percent of the dry matter

o f the hays. When analyses were made o f the sugar, starch , organic ac id ,

pentosan, alpha c e l lu lo s e and l ig n in contents o f the hay the undetermined

portion o f the to ta l hay ranged from 8 .6 to 18 .5 percent o f the dry m atter.

These percentages o f the undetermined portion o f the dry matter o f feeds

are w ith in the same range as reported by Ferguson (15 , 1 6 ). He id (42)

accounted fo r somewhat higher percentages o f the to ta l dry matter o f

fo ra g es.

122

A greater percentage o f the dry matter o f the immature orchard grass

hay was accounted fo r by the more d e ta ile d system o f a n a ly sis than in the

more mature orchard grass hay used in th is study* This trend has a lso been

reported by Reid (42)* D ifferen ces in the percent o f dry matter accounted

fo r in the immature and mature forages by th is system o f a n a ly s is may be

p a r t ia l ly due t© the increase in the proportion o f the dry m atter o f the

hay which the crude f ib e r and n itrogen -free ex tract fraction s represent

w ith in crea sin g maturity* The to ta l o f th ese two fra c tio n s increased from

61*9 percent in the immature hay to 76*2 percent in the mature hay. Errors

due to conversion o f the n itrogen content o f young p la n ts to p rotein equiv­

a len t may a lso be greater in young p lan ts than in o lder plants* I t i s a lso

recognized th a t th e undetermined fra c tio n includes any a n a ly tic a l errors

involved in each o f the in d iv id u a l analyses* With the proximate system o f

a n a ly s is th e se errors are included in the n itrogen -free exbract fra o tio n .

Several authors (2 , 19, 28, 43, 47, 52) have given summative analyses

o f woods th a t are remarkably c lo se to 100 percent o f the o r ig in a l m aterial*

Most o f th ese experiments have included the to ta l carbohydrate fra c tio n o f

woods in preparations o f h o loce llu lo se* There i s evidence th a t properly

iso la te d h o lo c e llu lo se reta in s nearly a l l o f the pentosans, a ce ty l groups

and the carbon d ioxide forming m ateria l o r ig in a lly present in the wood, (4 3 ).

Another approach to the summative an a lysis o f forages would be to include

sev era l ©f the carbohydrate fra c tio n s present in forages in a s in g le de­

term ination o f re la ted m ateria ls such as those included in h o lo c e llu lo se

p reparation s. The f e a s ib i l i t y o f such a system would depend upon su ita b le

techniques for i s o la t in g the h o lo c e llu lo se fra c tio n from forages and would

a lso n e c e s s ita te a knowledge o f th e d ig e s t ib i l i t y o f the various c o n stitu ­

en ts o f th e h o lo c e llu lo se fraction*

125

The l ig n in , t o t a l c e l lu lo s e , and pentosan content o f the immature

orchard grass hay was lower than th a t o f the mature orchard grass hay*

The organic acid content o f the orchard grass hay decreased with advanc­

ing maturity* The sugar content o f the most immature orchard grass hay

was lower than in th e hays cu t a t la ter stages o f maturity* The sugar

content o f the hays cut a t the three la ter stages o f m aturity progress­

iv e ly decreased w ith advancing maturity* The low sugar oontent o f the

immature hay i s probably due to i t s being placed on the bam dryer a t

a higher m oisture content than the other stages thus perm itting p la n t

c e l l r e sp ir a tio n to continue for a longer period than in the other three

stages which were p a r t ia lly dried in the f i e l d before being placed on

the bam dryer*

The d e ta iled composition of the crude f ib e r and n itrogen -free ex­

tr a c t fr a c tio n s o f the feces o f each animal used in the d ig estio n t r i a l s

i s shown in Table 28* The n itro gen-free ex tra c t in these feces ranged

from 35*7 to 44*6 percent* When a more d e ta ile d system o f an a lysis was

used in clu d in g the detezm inations o f sugars, starch , organic a c id s , pento­

sans, alpha c e l lu lo s e , beta and gamma c e l lu lo s e , and l ig n in , the undeter­

mined p ortion o f the fec es dry m atter ranged from 0*1 to 9*6 percent*

The more d e ta ile d system o f a n a ly s is aocounted for a h i$ ie r percentage

o f the dry m atter o f fe c a l m ateria l than o f the hays*

When orchard grass hays o f increasing m aturity were fed the alpha

c e l lu lo s e , pentosan and l ig n in contents o f the feces increased . The in ­

crease in the l ig n in oontent o f the fec es i s small compared to the change

in the l ig n in content of the hays since decreases in the d ig e s t ib i l i t y o f

the t o t a l dry m atter reduce t h i s change.

The content o f reducing sugars was very low in a l l o f the feces*

The starch content o f the fe c e s ranged from 1*2 to 3*8 percent and showed

124

about th e same range o f values for the three cows when fed each o f the

four orchard grass hays.

The c e l lu lo s e aggregate iso la te d from plant m ateria l by the Matrons,

S i l l s and Maynard (32) method includes a large part o f the hem icellu lose

and r e la ted m ateria ls ■which are fu rfu ra l y ie ld in g con stitu en ts and are

included in the pentosan fra c tio n in th is study* This does not permit a

summative a n a ly s is of the forage to be made using the crude c e llu lo se

sin ce i t would d u p lica te a p ortion o f the pentosan fra c tio n in the crude

c e l lu lo s e fraction* Determinations o f the pentosan content o f crude

c e l lu lo s e iso la te d by the method o f Matrone, E l l i s , and Maynard (32) were

made in order to c a lc u la te a "corrected Matrons c e l lu lo s e ” which was free

o f pentosans and would not cause d u p lica tion in a system o f summative

a n a ly s is which a lso included the pentosan fraction* Alpha c e llu lo se was

determined on separate samples o f crude c e llu lo se and the balance o f the

crude c e l lu lo s e which was not determined as alpha c e llu lo se and pentosans

was ca lcu la ted as beta and gamma ce llu lo se* These data are shown in Table

29* Apparently th e proportions o f alpha c e llu lo se and pentosans in the

c e l lu lo s e m aterial iso la te d by the Matrone, E l l i s and Maynard (32) method

does not change appreciably w ith increasing maturity* Furthermore, the

r a tio o f alpha c e l lu lo s e to pentosans in the crude Matrone C ellu lose

is o la te d from tlm fe c e s does not d if fe r greatly from th a t iso la te d from

orchard grass hay* The fra c tio n designated as the ”beta and gamma c e llu ­

lose" was ca lcu la ted as the residue from the crude Matrone C ellu lose th at

was not determined as alpha c e llu lo se or pentosans* This fra c tio n i s

qu ite var iab le in the amount present in various m aterials*

The content o f "corrected Matrone ce llu lo se" fo llow s the same trends

in the hay and the corresponding fe c e s as the crude Matrone c e llu lo se*

125

The apparent d ig e stio n c o e f f ic ie n ts o f th e various co n stitu en ts o f the

carbohydrate fr a c tio n and rela ted co n stitu en ts are given in Table 30. I t

i s ev id en t th a t the apparent d ig e stio n c o e f f ic ie n ts o f the crude Matrone

c e l lu lo s e , corrected Matrone c e l lu lo s e , alpha c e l lu lo s e , h o lo c e llu lo se ,

pentosans, t o t a l carbohydrate, organic acids and undetermined fra c tio n s a l l

decreased w ith advancing maturity o f the orchard grass hay. The d ig e s t ib i l ­

i t y c o e f f ic ie n t s o f the starch and sugar fra c tio n s were high with a l l o f

the four stages o f m aturity, A comparison of the apparent d ig estio n co­

e f f i c ie n t s o f the crude Matrone c e llu lo s e and the corrected Matrons c e l lu ­

lo se would in d ica te th a t there i s very l i t t l e d ifferen ce in the d ig e s t ib i l ­

i t y o f th e alpha c e l lu lo s e and pentosan fra c tio n s of the crude Matrone

c e l lu lo s e . A comparison of the apparent d ig e stio n c o e f f ic ie n ts o f the

t o t a l pentosan fr a c t io n o f the feed and the crude Matrone c e llu lo se in ­

d ic a te s th a t the pentosans not associa ted w ith the crude Matron© c e l lu ­

lo s e had a somewhat lower d ig e stio n c o e f f ic ie n t than the pentosans in ­

cluded w ith the crude Matron© c e l lu lo s e .

The apparent d ig e stio n c o e f f ic ie n ts o f the undetermined fra c tio n s

were ca lcu la ted by assuming th a t th ese fra c tio n s were o f the same com­

p o s it io n in the feed and fe c e s . The d ig e s t ib i l i t y of the undetermined

fr a c t io n o f the immature forage ind icated th a t th is fr a c t io n i s as h igh ly

d igested as the starch and sugar. The d ig e s t ib i l i t y o f t h is fra c tio n de­

creased w ith in creasin g m aturity and was d igested to about the same ex­

te n t as the alpha c e l lu lo s e in the most mature stage o f orchard grass.

A comparison o f the d ig e stio n c o e f f ic ie n ts o f the corrected Matrone

c e l lu lo s e , alpha c e l lu lo s e , h o lo c e llu lo se , and pentosan fra c tio n s o f any

one stage o f m aturity o f orchard grass hay would in d ica te th a t the d i­

g e s t i b i l i t y o f th ese groups are sim ilar enough to j u s t i f y grouping them

12 6

in to one fr a c t io n o f sim ilar substances such as mi girt "bo accomplished in

a h o lo c e llu lo se determ ination. The ob ject o f a more d eta iled a n a ly s is o f

the carbohydrate fra c tio n i s not to increase the a n a ly t ic a l determ inations

necessary but to a llo w in te l l ig e n t grouping o f various con stitu en ts in to

groups o f substances th a t would be sim ilar from an a n a ly t ic a l, b io lo g ic a l

and chemical standpoint*

SUMMARY

A more d e ta ile d system o f a n a ly s is th a t included determ inations o f

the sta rch , su gars, organic a c id s , pentosans, alpha c e l lu lo s e , and l ig n in

was used w ith orchard grass hay cu t a t four stages o f m aturity and the

corresponding fe c e s to study the con stitu en ts o rd in a r ily grouped in the

crude f ib e r and n itro g en -free extract fractions*

A greater percentage of the dry m atter o f the immature orchard grass

hay was accounted fo r by th is system o f a n a ly sis than w ith the more mature

orchard grass hay used in t h i s study*

Higher percentages of the dry matter were accounted for by the de­

ta i le d system o f a n a ly s is in the fe c e s o f animals fed the immature orchard

grass hay than in the fe c e s from animals fed the mature orchard grass hay*

Considerably higher percentages of the t o t a l dry matter o f feces were

determined by th is system o f a n a ly s is than were determined w ith the same

a n a ly tic a l techniques on the forage fed to these animals*

C ellu lose is o la te d from the orchard grass hays cut a t four stages o f

m aturity and from the corresponding feces by the method o f Matrone, E l l i s

Maynard contained approximately 25 percent o f furfural y ie ld in g con­

s t i tu e n ts c a lcu la ted as pentosans* apparent d ig estio n c o e f f ic ie n ts

o f the c e l lu lo s e corrected fo r pentosans was not appreciably d iffe r e n t

from the d ig e stio n c o e f f ic ie n t s o f the crude c e llu lo se fraction*

127

The apparent d ig estio n c o e f f ic ie n ts o f the crude Matrons c e l lu lo s e ,

corrected Matrons c e l lu lo s e , alpha c e l lu lo s e , pentosans, t o ta l carbo­

h yd rates, organic acids and undetermined fra c tio n s a l l decreased w ith

advancing m aturity o f the orchard grass hay. The d ig e stio n c o e f f ic ie n ts

o f the starch and sugar fra c tio n s o f the orchard grass hay were high w ith

a l l o f the four stages o f m aturity.

The s im ila r ity in the d ig estio n c o e f f ic ie n ts o f the alpha c e l lu lo s e ,

h o lo c e llu lo s e , pentosan, and crude Matrone c e llu lo se fra c tio n s in d icate

th a t a large part o f the forage th at i s ord in arily included in the crude

f ib e r and n itro g en -free ex tra ct fra c tio n s could j u s t if ia b ly be grouped

in to a h o lo c e llu lo se fra c tio n th at could be a n a ly t ic a lly determined*

128

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132

45.

46.

47.

48.

49.

50.

51.

52.

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T A B L E S

134

T ab le 27 .

Composition o f the crude Fiber and N itrogen-free Extract

Fractions o f the Feeds used for D igestion T rials on Various

Orchard Grass Hays

Orchard Grass Hay

Stage1

Stage2

Stage3

Stage4

No. 86 Grain

P ro te in 24.8 15.8 13.0 12 .4 9 .2

Ash 9 .3 6 .8 7 .1 7 .2 3 .9

Ether Ext. 4 .0 3 .5 3.9 4 .2 3 .6

Sugars 2.1 9 .5 5 .4 2.4 1 .4

Starch 1 .2 1 .4 0 .8 0 .9 65.0

Organic Acids 6 .3 6.0 5.4 5.0 —

Pentosans 15.1 15.8 16.8 18.1 6 .4

Alpha C ellu lose Beta & Gamma C ellu lose

19.5

3 .4

19.8

5 .4

19.1

3.8

27.7

2.5

2.3

Lignin 5 .7 5.0 6 .2 8.1 0 .5

Undete rmined 8 .6 11.0 18.5 11.5 7 .7

Crude Fiber 26.9 28.2 31.8 35.0 2 .2

N. F.E.Total , v Carbohydrates^1 '

35.0

49 .9

45.7

63.0

44.2

64.4

41.2

63.1

81.1

82.8

H olocellu lo s e ^ 46.5 52.0 58 .2 59.8 16.4

C1)T otal Carbohydrates * (Crude Fiber + N.F .E .) - (Lignin * Organi' Aci<

^ ^ H o lo ce llu lo se * Total Carbohydrates - (Starch + Sugar)

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136

T able 29*

The Crude Matrone C ellu lose Content o f Orchard Grass Hays and

the Corresponding Peoes and the D istr ib u tio n o f i t s Various Constituents

C onstituents o f Matrone C ellu lose

Crude Alpha Beta & CorrectedMatrone C ellu lose Pentosans Gamma MatroneC ellu lo se ___ C ellu lose C ellu lose (1)

O.G. Hay S¥g. 1

S tg . 2

S tg . 3

S tg . 4

34*0

34*7

37*7

40*3

/O 62* 6

61*0

61*7

67.5

/a26*3

28.6

25.8

26*4

11.1

10.4

12.5

6.1

25.1

24.8

28.0

29.7

Feoes Stage 1

X65

2408

H635

17.8

17.8

16.8

61.4

61.4

58 .4

25.1

25.1

24.4

13.5

13.5

17.2

13.3

13 .3

12.7

Stage 2 X65

2408

2J635

23.9

2 2 .2

21.8

57.9

64.2

55.5

25.4

27.4

22.6

16.7

8 .4

21.9

17.8

16.1

16.9

Stage 3 X65

2408

H635

26.6

26.2

27.1

61.6

61.7

61.6

25.4

25.7

25.2

13.0

1 2 .6

13.2

18.8

19.5

20.3

Stage 4 X54

2408

N635

27.7

27.1

27.2

67.1

63.5

60.8

26.8

24.2

24.7

6 .1

12.3

14.5

20.3

20.5

20.5

137

T ab le 3 0 .

A pparent. D ig e s t io n C o e f f i c i e n t s o f C a rb o h y d ra te s and R e la te d C o n s t i tu e n ts

in O rch a rd G rass Hay C ut a t Four S ta g e s o f M a tu r i ty

S ta g e and Cow C

rude

Cel

lulo

se

Cor

rect

edC

ellu

lose

Alp

haG

ellu

lose

Hol

o-

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se1

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Sta

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otal

Car

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drat

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Org

anic

Aci

ds

Und

eter

min

edF

ract

ion

S ta g e 1 X65 82 82 80 82 78 97 96 86 -55 95

2408 82 81 80 83 79 94 97 87 52 99

N635 83 82 82 83 79 98- 94- 88 55 94

A'v. 82 88 C l 70 96 96 87 53 96

S ta g e 2 X65 77 76 78 79 72 95 99 84 60 91

2408 79 78 77 79 75 95 98 85 58 82

N635 79 77 78 79 74 97 98 86 52 92

Av. 78 77 78 79 74 96 98 85 57 88

S ta g e 3 X65 72 73 69 73 64 97 98 79 52 85

2408 72 72 68 75 66 93 99 81 49 90

N655 72 71 69 74 67 97 98 82 48 87

Av. 72 72 69 74 66 96 98 81 50 87

S ta g e 4 X54 70 70 73 69 64 97 95 77 46 69

2408 69 68 73 69 63 94 93 76 45 77

N635 69 68 71 68 62 97 95 77 44 75

A v. 69 69 72 69 63 96 94 77 45 74